Where to pick up rental car after stay in London?

If you are going to Bath by car, make sure that your hotel can provide free parking as on street parking can be expensive. I think it would be best if you arrive in Bath by train and hire the car prior to leaving. Use www.nationalrail.co.uk to find trains (PAD > BTH) & pre book specific train about 10 weeks ahead at www.gwr.com

Click this link & you should see a map of Bath. (The colours on the roads refer to traffic flows - live; so if you view during the British nighttime, you will not see any congestion - shown in red/orange). You should be able to se the rail station - which is right in the middle south. Click on the yellow man and drag and drop on the street for street view. I would suggest that you do this for other locations which you intend to visit - though I prefer to use Google earth.
https://www.google.co.uk/maps/@51.3821569,-2.368736,2966m/data=!3m1!1e3!5m1!1e1

If you have never driven in Britain before, take the train to Bath and rent a car there. If you have driven on the left and feel comfortable with city traffic, there are some rental agencies near Paddington that have easy access to the A40 Westway, which is a limited access highway that can get you out of London relatively quickly (depending on traffic).

If you are going to be there for three weeks, consider leasing rather than renting a car--although you'll probably have to pick it up at an airport. I'd get an automatic.

Take the train to Bath and rent the car as you are leaving. Parking, to quote one of my college profs, is a bitch. And he never swore.

there are some rental agencies near Paddington that have easy access to the A40 Westway, which is >a limited access highway that can get you out of London relatively quickly

do note that the Westway is short, has a low speed limit but looks much faster (watch the cameras), and drops you right back onto a traffic light and speed camera laden fairly narrow 4 or 6 lane normal A road (watch both the traffic light cameras and speed cameras in their new pint-sized tiny boxes) and it stays that way until just before the M25 (watch the speed camera at the top of the hill after the McDonalds just before the low speed area becomes derestricted).

Thank you for your thoughtful replies.

To answer some of your questions, our guesthouse, The Ayrlington, does have parking for us. It is on Pulteney Rd South, which is the A36 according to the link James provided.

My husband has driven in Ireland several times and doesn't mind, but has not driven in England, if that is much different.

We'll be leaving London on June 6th, and probably will drop the car off in Edinburgh the day we arrive for a 3 night stay. We don't plan to use it while in Edinburgh. That would mean we'd have the car 18 or 19 days, depending on whether we drive or take the train to Bath. I'll check out a lease compared to a rental. Is there much difference in the paperwork? We've rented lots of times but have never leased before.

I'll do some research on the trains now that our holiday company has gone.

And Nigel, thanks for the warning about the traffic cameras, all things we'll take into consideration.

Thanks!

I'd suggest taking the train to Bath, as suggested, and renting the car there. Nigel's "deconstruction" of Westway is just an example of why driving in or near London should be avoided if possible.

Bath itself is walkable and a car would be a nuisance, but you'll need it for your side trip and of course to go north.

As for dropping it off in Edinburgh, I'd suggest using Auto Europe and a map or Google Earth to locate a dropoff point for the company you're renting from. (Auto Europe is a US-based broker, a good way to find cars and to rent them if you don't want to deal directly with the rental company. In this case, it would help with the search whether or not you use it for the rental.) EDIT -- You might try posting your Edinburgh drop-off question in the "Scotland" forum here, to get more responders with local knowledge.

I doubt if a lease would make sense for the time you have.

If you are driving out from London, you could do Salisbury (Cathedral) & Stonehenge on the way to Bath - as long as you leave London by about 9.40am. To do this, you need the M3 out of London but for Bath direct, the M4.

If you outline your intended trip, you might get people chipping in with advice.
https://www.travelsupermarket.com/en-gb/car-hire/

Since you are going to Bath after London, take the train from Paddington to Slough. There are several different car rental companies in Slough.

Lots of great suggestions, thank you. If we pick up the car coming out of London, the idea of taking the train Slough to get it looks interesting as a way to avoid some of the London traffic. AutoEurope doesn't seem to operate out of there, although EuropeCar does. I wonder if they didn't give me results because of dropping it off in Scotland? I wouldn't think that was the case, but the results from AutoEurope were "Sorry." I/We need to buckle down and figure out what we want to do. Taking the train all the way to Bath sounds good, too, then picking it up after a day or two. I have checked the links you all have provided and find them very useful. I will post our itinerary soon, but am still wrapping up holiday things here.

A few other thoughts - Do you drive manual transmission , and if so , will you feel comfortable shifting with your left hand ? If the answer to either or both of these is no , be aware that automatic transmissions are not as ubiquitous in Europe as they are in the States.. If you want an automatic , picking the car up at Heathrow provides you the best chance ( with an advance reservation ) of getting one. Picking the car up in Bath might be more of a crapshoot. Drop off is dictated by the location of the rental agency . On my trips to the UK , I have had no difficulty picking up at Heathrow and dropping off at Glasgow or Edinburgh . ( Avis via AARP ) I am of a certain age .

Here are three car rental companies that you can pick up in Slough and drop off in Edinburgh.
Europcar, Enterprise and Hertz

On our second trip to England, we picked up our rental car at Heathrow and drove to Bath directly. We do have a GPS and getting out of Heathrow is very easy.

Thanks all. After doing some research and talking about it, we think we will take the train directly to Bath on the early side (after having spent 5 days in London) and spend the rest of the day exploring Bath. We'll then pick up a car there, and do some exploring over the next day or two, depending on how much time we decide to devote to Bath.