Itinerary Critique

It strikes me as a lot of driving in what is effectively nne days. You will be driving more than sightseeing.
Cornwall is a long way on not very fast roads. I would drop that. If you do go, be aware that parking is difficult to impossible, including in accommodation.
Six adults plus child plus luggage means a van, again, not so easy on rural roads.
Consider dropping Cornall, train to Bath, local tours from there.

I agree with Lin—It's a tightly packed itinerary, and you will spend a lot of time going from place to place rather than actually enjoying the sights. Also, like she said, I would skip Cornwall and Devon. It is very difficult to drive there (especially Cornwall) and given that you have seven people, you will need to get either one really large car or two smaller ones, which makes it even more difficult. For what it's worth, I've driven all over the UK, and I found Cornwall the most difficult to drive in. Plus during the summer, it gets extremely crowded.

I would stick to Bath, the Cotswolds and that area, as you will find plenty to do there, and it's very charming. That's why it's so popular. Your London schedule looks fairly tight as well, and with a nine-year-old, I'd be wanting to stretch things out a little bit more. If you remove Cornwall and Devon, though, that gives you an extra two days that you could tack onto Bath and/or London and it would make for a very nice trip. You wouldn't be able to see very much anyway in two days in Cornwall. It's so crowded that driving is very slow going, and it can take you forever to get from place to place.

I also like Lin's suggestion of doing day tours from Bath to the Cotswolds and other places OR you could rent a car once you get there. Again, with seven people, you're going to find it tough to get a vehicle that works and can hold all your luggage. Instead, you could travel by train to Bath, and use it as a base to explore the surrounding sites, like the Cotswolds, Stonehenge and even Blenheim and Oxford. Then rent a car after you get there. That way, you wouldn't have to worry about finding room for all of your luggage in the rented vehicle. Turn in the car before you leave and take the train back to LHR.

Or another solution would be to return the car in Oxford, explore the city on your last day, and then take the Airport Bus that goes directly to Heathrow Airport. That way you avoid having to go into London proper at all at the end of your trip.

We have visited all the places you listed and they are great.

1) Consider renting a car to pickup in Oxford rather than going back to Heathrow.
2) Not sure you can do both Highclere and Stonehenge in route to Bath. Do some research and check the times that you can book to visit both. I remember than Stonehenge is extremely crowded, requiring parking some distance from the site taking more time to visit.
3) Your plan to drive in Cornwall and Devon is way more a problem. We did a great five day tour of Devon and Cornwall from near Victoria Station last year with Rabbies Tours. It was fantastic and we found so much to see there. You only mention Tintagel Castle and Port Isaac, which ignores much more. Check the itinerary for the Rabbies Tour and you will see what I mean. Key places are Land's End and St Michael's Mount are must sees. Also, Port Isaac was nice, but probably the MOST congested and crowded place in Cornwall. Driving there, parking there is a nightmare.
4) We stayed in Chipping Campden at the excellent Volunteer Inn for six nights, did two full days visiting the Cotswolds as well as day trips to Oxford, Blenheim Palace and Stratford upon Avon. Your plan for the Cotswolds need more research and planning.

You may wish to do the Tower of London on a morning when it first opens rather than on the day of arrival when you are jet lagged and tired. We enjoy just walking in Kensington gardens, and your 9 year old may like the Princess Diana playground for the first day. A Thames river boat cruise and the London Eye would be another possibility for the first day.

Good suggestion to drop Cornwall and Devon. The roads are very narrow there and what looks like hedgerows are actually often stone walls. GPS was not accurate for directions when we went. It often said unnamed road, so it is easy to get lost. If you drop Cornwall you could add an extra day in London at the beginning to see the Tower of London on another day.

Going from Bath to the Cotswolds was a good suggestion also.

You have a very nice list of sites, however, I say this as someone who likes to pack a lot in- there is way too much in this itinerary and I don't think it's very doable. A few thoughts from me:

-I wouldn't plan on any big sites the day you arrive, you will be tired after an overnight flight. The Tower of London is, in my opinion, the best site in London and it's huge so you will want to be awake for it.
-When you say Westminster, do you mean the neighbourhood? There's quite a bit to see as it's the central area of London. If you mean the abbey, I think the abbey, Churchill War Rooms, and British Museum is too much in one day- I would just select two of those.
-Highclere, Stonehenge, and driving to Bath is also a lot for one day- it's doable but I would just do one.
-It's a long drive to get to Cornwall and the motorway ends after Exeter- that would be a lot of driving just for two nights.

If you drop the Cornwall piece, you could do this all by train- London to Salisbury to see Stonehenge (there's a bus from Salisbury to the stones), then Salisbury to Bath, Bath to Moreton-in-Marsh (there are buses to Bourton-on-the-Water and Stowe-on-the Wold), Moreton-in-Marsh to Oxford (you could either just visit Oxford or get a taxi to Blenheim- then on the way back a taxi to the closer station Oxford Parkway) and then back to London. But, you know your own pace- I would just think about paring back a bit. Good luck with your planning!

Hi
I would change up the order slightly.
Day 3 - pick up car then visit either Stonehenge or Highclere ( need reservations and not open every day so this could determine things ). Then drive towards Cornwall. I would stop around Okehampton but the key will to find suitable accommodation for 7.
Day 4 - Visit Port Isaac and Tintagel returning to your lodging in Okehampton.
Day 5 - visit the spot you missed in day 3 and on to Bath arriving in lare afternoon.
This should break up your drives into shorter chunks and keep driving time to around 3 to 4 hours a day.
Day 6 - Bath.I enjoyed the Mayor’s free guided tours.
Day 7 and 8 - Cotswold and Blenheim.
Day 9 visit Windsor before car drop off.
If Highclere was not available on Days 3 and 5, you could try the morning of day 7.
Enjoy

The 9 year old will probably need a car seat, so make sure to book one when you book the car. In the UK if you ask for a van, this is a small commercial vehicle without any windows... You need to ask for a MPV or people carrier. Make sure what you hire will seat 6 plus child and still have room for all your luggage..

I also feel this is a lot of driving in a short time. I'm not sure the one day in Cornwall actually merits the day it takes to get there and another day to get back. I'm also not too sure how child friendly this is for the 9 year old (but you will know your child's interests and boredom levels better than us.)

What time would you anticipate arrriving at Tower of London on the first afternoon? Will you be off an overnight flight and if so how much will people have slept on the plane? It is recommended to allow 3-4 hours for a visit (and in the afternoon there may be quite long queues for the crown jewels. There is an argumentt for doing this the next morning.

What do you mean when you say Westminster - is this Westminster Abbey? If so that combined with Churchill War Rooms and British Museum if time permmits is a pretty hefty day intellectually. You may be pushing it toi do all three.

When are you intending to visit and have you checked opening times for Highclere Castle. Summer visiting times for 2026 are Sunday 12th July 2026 – Thursday 3rd September 2026, but they are closed Friday and Saturday each week. Next year will probably be similar. They also have three admission times - between 10:00am – 12:30pm, 12.30-2.30 and 2.30-4.30.

If Highclere Castle is a priority you may need to plan your itinerary around this.

You may find your plan of driving from Heathrow to Highclere, Stonehenge and Bath is ambitious depending what time you get away from Heathrow and traffic.

I think you need to rethink your plans. Cutting out Cornwall does give more time to actually see and enjoy places.

Rather than heading to Bath after London think about visiting the Cotswolds first (Allow two nights, possibly planning to stay in or around Bibury area, as this is closer to Bath) ). You can still pick up the hire car at Heathrow or catch a train to Oxford from Paddington and hire a car from Oxford. Visit Blenheim Palace the day you arrive - there's lots to see and do so it will effectively take a full day. Spend a day pottering round the Cotswold villages

Then head to Bath and spend 2 nights there.

Then head south - EITHER TO Dorset area - The ruined Corfe Castle doesn't have the King Arthur connection but is pretty good. There are also many attractive small villages as well as places like Lulworth Cove and Durdle Door. OR head to the New Forest (attracticve small village and New Forest ponies) for 1-2 nights.

Both of these are attractive but don't yet feature on the typical tourist itinerary.

Return to London via Stonehenge and Highclere castle. drop off car and stop at hotel near LHR

If going to Cornwall I would go further to Wadebridge, and stay at the Premier Inn, just on the edge of town.

For either Okehampton or Wadebridge once you come off the M5 at Exeter it is the dual carriageway A30 all the way, so assuming no traffic issues a high quality and fast road.

The PI, being on the edge of town, has free parking, and plenty of it- and you can always nip into Wadebridge for your meals (and a cute little movie theatre). A bit of a shame the American diner has gone, but plenty of English options.

The benefit of Okehampton would be that the White Hart Hotel has rooms for 5 people (4 adults and a child- double bed, two singles [or 2 doubles] and a child sofa bed)- so you would only need 2 rooms- a room for 5, and a twin or double.

From Wadebridge the roads are not at all bad to Port Isaac and Tintagel- about 16 miles from Wadebridge to Tintagel, they are not the kind of nerve wracking single track roads being pictured. You get full sized buses and delivery trucks on them with ease, as well as cars. If you've driven in Ireland and Scotland they don't or shouldn't pose a challenge.

Port Isaac is the pinch point for parking, but the village is a lot quieter now than it was, now the series has finished.

Yes it feels like a very long diversion to see so very little of Cornwall, and little or nothing of Devon except a main highway, not how I would suggest is the best use of time, given the far closer Dorset as an example. But if your heart is totally set on it, that seems a good way to achieve it.

You say you are planning to visit next summer. The school holidays for English schoolkids runs from about the last week in July to the first week of September. Things will be quieter outside this period. Cornwall and Devon are very popular holiday destinations for Brits.

As others have said. you'll spend a long time driving to PI and Tintagel. The former, in particular, is a tiny village - very picturesque but not much to do there. It's been a while since i have been to PI but there was a new car park on the edge of the town - there may be a bus into the centre. There is very little parking in PI itself. There is more parking in Tintagel, and out of school holidays I think you'd get parked most days.

One thing - I recall reading that none of the council-owned car parks in Cornwall now accept cash payments of parking charges. typically, you need to pay by a parking app on your phone. This is getting pretty common across the UK and you'll need to have a phone that is able to access these apps. There are several such apps and each of the different councils may only use one of them, so you may need to register with several. Get screenshots of payment confirmations as payments for hire cars are not always applied correctly. Like speed limits and driving in bus lanes, charges for parking are now often enforced via number plate recognition systems, so check the parking rules even in apparently rural locations. If you do pick up a fine, by the time it has been forward via the car hire firm any early payment discount option will have expired and the firm may well add a hefty 'admin fee'.

We have just come back from two weeks in Cornwall, so have some up to date experience on car parking. Whilst I don't recall any car parks that took cash I think every one took payment by contactless card as well as by parking app.