itinerary critique and advice sought

The itin is quick paced to cover alot of territory since u are driving perhaps uncould ck the miles - time betw stops.
Www.viamichelin.com
I find the driving in england always takes longer than i anticipate and is fatiguing due to right hand drive etc.
the portion of wales to keswick and some of scotland seems alot of driving. Aberdeen is a long drive north.
As an option u might consider only going as far as edinburg and omitting wales this trip.

I can't see the point of hiring the car on the first day in Bath. You will have jet lag and in any case, Bath can be easily walked around -
for the most part. (It also has expensive on-street parking).

Note that you could take the Railair coach to Reading for the trains to Bath rather than go via Paddington. www.nationalrail.co.uk - fares are cheaper when booked about 8 weeks ahead but this can tie you to specific trains.

If you were able to go on the Mad Max tour on day 2, then that is another day of car rental saved. Of course, you could drive this yourself in the rental car. Trains also run from Bath to Salisbury - (see the medieval cathedral) from where shuttle buses go to Stonehenge. http://www.thestonehengetour.info/route

I don't think much of Glastonbury. If you go to Wells by hire car, I would take a detour to nearby Cheddar Gorge (also has showcases).

On May 24 you could cover more Cotswold villages. Add these:> Bourton-on-the-Water, Lower Slaughter, Broadway, Chipping Campden & Hidcote Manor Gardens. Snowshill - if time.

May 25 - It takes about half a day to see Blenheim Palace. I have only seen Warwick Castle from the outside. Consider also throwing in Stratford-upon-Avon on this day - but it is pushing it.

Not sure about Aberdeen. It is not in the most scenic part of Scotland. From Inverness, I would be more inclined to use the A9 to Edinburgh via Pitlochry. (This would save you a day). I have not been to the Aberdeen area so perhaps others will correct me if I am wrong.

The day saved could be used to visit Northumbria when going S from Edinburgh. Bamburgh Castle? Alnwick Castle? Alternatively, you could ditch the car in Edinburgh & then use the train to York (1 night) & then train to London (Kings Cross).

You might find my earlier response of interest regarding getting from the Cotswolds to north Wales:> https://community.ricksteves.com/travel-forum/england/choosing-a-second-week-in-england-or-wales

I agree about moving your days in Bath and doing the Mad Max day on Day 2. Take public transport to Bath. I am not big on the recommendation to drive to Bath after a flight from the US. Seems unwise as you may be jet lagged.

I also am not the driving expert but to me Nevern is too much to do on that day as it's much further South. I did find the cross in situ, the bleeding yew and the ogram writing on the stones inside the church very interesting but it's maybe a 30-45 minute stop. If you do go, notice the large stone bridging the stream behind the church. A guide told me it is a bluestone of the same type as used at Stonehenge from the nearby Preseli Mountains.

Please note that 2 similar sounding places are found in Wales:>
NEFYN is in NW Wales on the Llyn peninsula. I have been through this village on my way to Morfa Nefyn from where I walked around the bay to Porth Dinllaen - on a boiling hot day so went in sea to cool off. Absolutely beautiful on a nice day!

NEVERN is in SW Wales (between Cardigan & Fishguard) and a long trip from your base in north Wales so not advised. Here is the church at NEVERN:>http://www.castlewales.com/nevern_cross.html

I would consider a visit to Portmeirion whilst in North Wales.http://www.portmeirion-village.com/visit/

I suggest you use the AA site as a route planner. If you put in for Stow-on-the-Wold to Conwy, it will just show you the quickest route - mainly via motorways (like Interstates). If you wish to follow my touristic route, it will be slower & to figure out how long it takes, break it down into sections on the AA route planner. http://www.theaa.com/route-planner/index.jsp

This is too much for me, and my husband (who is the driver in our family) would flat out refuse to drive this much. Your days will be packed with driving and seeing sites and I don't see much room for downtime. If you like this kind of fast paced travel, then you'll probably be fine. Just accept that there are bound to be days when you don't get to do everything you planned due to traffic jams, getting lost, etc. So prioritize your sites so you don't miss your top priorities. Also, be sure to check all the travel times on Michelin or similar site, add in some extra time for heavy traffic and construction, then make sure to allow time for finding the place you are staying, checking in, etc. Also, you need time to eat.

You might consider dropping Aberdeen (I have not been, but it's out of the way) and Wales (I adore Wales but it deserves more time; also it's an outlier and I don't think you'll be able to fit all that in) to add more time to other places, such as York. I don't think you've allowed enough time to actually see York.

You've got a lot of fabulous places on your itinerary; I hope you have a great trip!

Too fast for me too, I'd slow down to experience more than highways. Good advice above about taking the train to Bath, avoiding car rental fees (and the LHR surcharge) till you actually need the car. And maybe not such a great idea to drive on the left on your jet-lag day.

I'm a big Hadrian's Wall fan but you've got it on there twice, out of Keswick and again on your way down from Scotland. I won't say "if you've seen one end you've seen them both," because I haven't, but one visit should really be enough.

I don't know all the sights you've got listed between Inverness and Edinburgh, maybe an overnight in Aberdeen makes sense, but it's pretty far out there. So is Skye, but at least it's world-class scenic.

And I agree that you could drop the car in York and train into London, saving time and energy.

I tried to make this work in the time available, but couldn't accommodate the Lake District and Aberdeen.

May 21 Arrive LHR, train to Salisbury (1 nt)
May 22 Pick up car, drive to Bath (1 nt)
May 23 Cotswolds (2 nts)
May 25 Oxford (1 nt)
May 26 Stratford-upon-Avon (1 nt)
May 27 Conwy (2 nts)
May 29 York (1 nt)
May 30 Durham (1nt)
May 31 Edinburgh (2 nts)
June 2 Pitlochry (1nt)
June 3 Inverness (1nt)
June 4 Skye (1nt)
June 5 Drop off car, sleeper train from Fort William to London
June 6 London (6 nights)
June 12 Fly home

Is it better economically to fly in to Edinburgh and then fly home out of London...instead of flying to London and then going by train or plane to Edinburgh?

Whether or not it's more economical to fly an open-jaw/multi-city ticket (in to one city and out of another), it certainly saves time. I'd definitely price it out, but even if it were more expensive I'd almost always choose to fly open-jaw to save time and hassle.

Open jaw, in to London, out of Edinburgh ...

May 21 Arrive LHR, London (5 nights)
May 26 Train to Salisbury (1 nt)
May 27 Pick up car, drive to Bath (1 nt)
May 28 Cotswolds (1 nt)
May 29 Oxford (1 nt)
May 30 Stratford-upon-Avon (1 nt)
May 31 Conwy (2 nts)
June 2 York (1 nt)
June 3 Lake District (2 nts)
June 5 Fort William (1 nt)
June 6 Skye (1 nt)
June 7 Inverness (1 nt)
June 8 Pitlochry (1 nt)
June 9 Edinburgh (3 nts)
June 12 Fly home