Edinburgh to Heathrow via Lake District and Wales

Cardiff is easy to reach by train. There is a bus from Cardiff to St. Fagan's Folk Life Museum. You can also get to Caerphilly Castle from Cardiff using public transportation.

For the lake District, consider staying in Keswick. With no rental car you will be at a severe disadvantage in The Lake District.

Do the circle around the lake from Keswick -it is described in Rick Steves guide to Great Britain.

For Wales, you have the choice of visiting North and/or South Wales. For North Wales (just before visit Chester with loads of Roman History). then on the Conwy with its historic castle built by Edward I.
https://visitnorthwales.co.uk/things-to-do/
Snowdonia National Park is beautiful.

South Wales is just as amazing. It is loaded with castles.

https://wales.org/destinations-in-wales/south-wales/
Also, Tintern Abbey is worth a stop. Chepstow Castle, Cardiff Castle, Caerphilly Castle (a short train ride from Cardiff), Pembroke Castle and Raglan Castle.
https://museum.wales/stfagans/

Also, Tenby is a great seaside town for a couple of nights and St. David's on the SW point of Wales is very historic and a must see.

EDITED TO CORRECT THE TYPO referenced below (Thanks, John)

See this recent thread for lots of detail about Hadrian's Wall and the Lake District.

https://community.ricksteves.com/travel-forum/england/lake-district-by-bus-train

Book your accommodation first then worry about the trains.

As that post makes clear public transport in the lakes is easy, frequent and cheap. I don't know why people persist in saying otherwise. I live in the Lake District.

When the summer lakes bus timetable comes out in 5 to 6 weeks time it will be posted in this forum.

For Hadrians Wall catch a very frequent train from Edinburgh to Newcastle (takes slightly over the hour), change at Newcastle for a 1/2 hourly train to Hexham or Haltwhistle (takes about 30 minutes).
I'd say 2 nights here. I assume the tour ends at breakfast on the 16th so transfer to the wall that day.
Then 1/2 hourly train Hexham to Carlisle (45 minutes), changing to a frequent train to Penrith- takes 15 minutes (bus to Keswick for the north lakes, takes 45 minutes) or Oxenholme (change for Windermere for the south lakes)- 45 minutes CL-Ox, 20 minutes Ox-Wm.

Either town is as good as the other.

I'd say 4 nights here.

Then back to Penrith/Oxenholme- hourly train to Crewe (Carlisle to Crewe is around 2 hours), change there for hourly or better train along the North Wales coast or hourly direct train to Cardiff -takes 3 hours.

Others can debate North/South Wales with you. But 4 nights there.

North Wales to London Euston has direct trains. Cardiff to London Paddington is 3 hours, every hour.

I'd argue for Cardiff then you end up where you want to be without a tube transfer from Euston.

A nice easy, balanced itinerary.

If the trains go on strike then EDI to the wall and then the Lake District is easy (National Express to Newcastle at 0845 or 1045, then buses as detailed in the post).

Likewise there is a coach from Penrith to Cardiff at 1150 daily, 2 hour change at Birmingham, arrive Cardiff 8.40 pm, and a coach every hour or so from Cardiff to London- 4 hour journey.
So that is a robust plan.

We'll give you any constructive help needed on fares when you have determined your plans, if required.

Keswick is probably the best place to stay in the Lakes - a lovely small town with full facilities and access to many walks without a car. Also have a look at Mountain Goat tours - they have a fine reputation for small bus day tours of the Lakes.
But note that it does not have a railway station. From Edinburgh you need a train to Penrith and then a bus to Keswick. And then in reverse when you leave.
From Penrith you can take a train to North Wales to enjoy the delights of Snowdonia NP. Take the train to Conwy or Llandudno with a change at Warrington or maybe Crewe.
From there is an awkward journey down to South Wales, but they’re a regular train down to Cardiff - slow but it passes through some lovely countryside on the way to Cardiff. I would recommend a stopover in Ludlow, although that’s in England, it’s in some stunning country, way better than the much hyped Cotswolds. Another good stop further south would be Abergavenny. Both Abergavenny and Ludlow have great foodies reputations.
Then down to Cardiff and then a train towards London. You could stay in the Paddington area where the Cardiff train terminates but I wouldn’t use the HEX. You have already missed the window for the very cheap tickets for June and there is the new, cheaper and perfectly acceptable alternative of the Elizabeth line.
Another alternative would be to divert to Windsor and have a relaxing night there, just a short taxi ride to Heathrow.

Isn31c offered some more excellent advice whilst I was typing but there is I’m sure an unintentional typo in there. It’s about 2 hours from Carlisle to Crewe, not 12! But, as I said it might be quicker to change at Warrington anyway.

PS- I'm steering clear of the HEX/Elizabeth line debate which is endlessly talked about on this forum!

By the way there is a coach about every 90 minutes from Cardiff direct to Heathrow- given your early departure time next day, which will be check in around 0830, why not take the 1140 coach, arrives LHR 1430 and book an airport hotel for the night. Saves any stress next morning.

Consider going by train from The Lake District to Chester (1 change needed en route). Chester is a lovely historic small city. Direct trains go from Chester to Cardiff roughly every other hour and take around 3 hours for the trip. On this line, Ludlow is worth a hop off to have a look around for a couple of hours. (Usually about 3 trains an hour from Ludlow to Cardiff and you would have to split the ticket if hopping off here). Trains from Cardiff to London (Paddington) take 1 hour 50 minutes. If you wanted to go to Windsor for your final night to be near Heathrow - take train from Cadiff to Reading & another to Slough where you catch the branch line shuttle to Windsor.

Another alternative is to go by train from Lake District to Chester - have a look around (though it is quite a walk to centre from station) and then another train to Llandudno where you stay maybe 2 nights. See Conwy castle and Llandudno and Bodnant Gardens.

Leave Llandudno by train for Blaenau Ffestiniog and then Ffestiniog steam railway to Porthmadog (Premier Inn would be a good place to stay) . https://www.festrail.co.uk > you could use the Welsh Highland Railway to Caernarfon (Castle) but if you want to do a bit of hiking, alight at Rydd Duu and walk northwards. Nearby Portmeirion would also be worth a visit from Porthmadog.

Leave Porthmadog from ’normal’ train station - which as the north end of town - and take train to Barmouth for optional stop -. then take next train to go all the way to Shrewsbury - have a look around before catching a train to Cardiff. (Could stop at Ludlow if time).

This is the ’normal' line that connects Porthmadog. https://www.thecambrianline.co.uk
https://www.railcard.co.uk
https://www.nationalrail.co.uk (but also check the split ticket sites below).

Hopefully this will be useful guidance. Google the places mentioned to help you decide what will be right for you given the time that you have. Any longer train journeys (such as Cardiff to London) will be much cheaper if you can pre-book specific trains. Some train journeys are cheaper with split tickets. https://www.traintickets.com/? /https://trainsplit.com
https://www.traveline.info is useful for finding buses.

Sound advice given in next post (below) regarding buying a pass for Wales.

That sort of itinerary is ideally done with a 4 day in 8 Explore Wales Pass-
https://tfw.wales/ways-to-travel/rail/ticket-types/rovers-and-rangers/explore-wales

That includes most bus routes in Wales, and gives a discount on the Heritage Railways. Validity starts at Crewe (in England) and at £25 per day is far better and easier than buying individual tickets which are time limited.
You just get on and off at will.

For instance Chester to Cardiff with time in Ludlow is £40 alone on time specific trains- £76 on an open single ticket which allows unlimited stops on route during the date it is valid for.

Mountain Goat offers one day tours in the Lake District and Northern Wales. I took a one day tour with them. The driver/guide was okay but I did get to see quite a bit of the area.

Rabbies also offers tours but out of Edinburgh. Their three day tour of the Lake District leaves and returns from Edinburgh. However, on the return, you could see if they could drop you at the Penrith train station for your continuing journey south.

Rabbies also offers a one day tour out of Edinburgh that includes Hadrians Wall.

The bus service in Northern Wales was very good and I could easily visit the larger towns using it. Conwy or Bangor would be good places to use the bus service and any local one day tours. When I visited I split by stay between Conwy and Caernarfon.

Thank you all for your suggestions.
Using them, I have put together the following plan (with a couple more questions):

16: Edinburgh to Haltwhistle

17: Hadrian's wall

18: Haltwhistle to Carlisle to Penrith to Keswick

19 & 20: Walk in Snowdonia NP and other sights TBD

21: Keswick to Conwy:
Bus to Penrith;
Penrith to Chester (via Warrington or Crewe?); Chester to Conwy - do I have to change in Llandudno Junction for Conwy?
Can I buy the Explore Wales ticket in Chester?
Can I use my 2-1 railcard to buy the Explore Wales ticket for £65.35?

22 & 23: TBD

24: Conwy to Chester to Cardiff (arrive with time to explore the town);
Can I use the Explore Wales ticket for this trip?

25: Guided trip from Cardiff to Tenby

26: Guided return to train station in Swansea for trip to London (hotel in Paddington area)
Can I use the Explore Wales ticket for all or part of this trip?

27: Paddington to Heathrow T3

19 and 20- You mean walking in the Lake District NP, rather than Snowdonia NP.

Purchasing Explore Wales- you can purchase it at any UK ticket office for the £65.35 railcard discount. So you could buy it at Edinburgh or Penrith, if you wanted!

That might surprise them, especially Penrith, but it can be done.
If you didn't do so earlier then at Crewe as that is a boundary station.

Route via Crewe, rather than Warrington. The TfW train from Warrington to Crewe isn't included in the Pass, but it is valid on TfW and Avanti trains from Crewe. You need to change at Chester or Llandudno junction for Conwy as only trains on the Cardiff or Birmimgham (alternate hours) to Bangor and Holyhead route stop at Conwy.
Yes Explore Wales is valid Conwy to Cardiff (should be a through train unless you want to break journey at Chester, as you are entitled to do).
On the Swansea to London train it is valid on the London train run by Great Western as far as Newport (Gwent). Pre-purchase a ticket from Newport (Gwent) to London and you don't have to move from your seat.

BTW I have posted the Lake District summer bus timetable today, hot off the press, on this thread
https://community.ricksteves.com/travel-forum/england/summer-bus-services-in-the-lake-district-summer-2023