Portsmouth to Cotswold Region

Lisa,

I can definitely understand your wanting to pick up your rental car outside a big city. Am I correct in guessing you plan to rent an automatic? In that event, one thing to keep in mind is that a smaller rental car facility may have fewer automatics. I have rented cars at Stoke on Trent, Bath, and many times at Heathrow - - - I don't know what's available in the Portsmouth area. Your best bet may be to rent the car in Portsmouth.

Re best route from car rental location to the Cotswolds, I recommend you use a GPS once in England, but you can also check it out in advance using this website (British equivalent of AAA). Click on Route Planner in top right.
https://www.theaa.com/

Google Maps shows a Europcar location just south of the Portsmouth Historic Dockyard (museum) area. I hope you'd have time to visit some of those attractions. From there, you can get really quite directly onto the motorway. There are additional rental agencies about three stops down the rail line at Hilsea station, but I don't see any advantage to that location.

Are you driving straight from Portsmouth to the Cotswolds in one day, or are you looking for suggestions of places to visit en route? Your route can easily take you past Stonehenge, for example.

Also, do you want to drive on major highways (motorways) or on country lanes? Adjusting to driving on the left is easier on the motorways, IMO. There's no single motorway running straight between Portsmouth and the Cotswolds, but timewise it's about equal because driving on the country lanes you'll have to go much slower, and there's always the risk of taking a wrong turn at one of the many roundabouts.

take a taxi from Portsmouth to Southampton AIrport where you'll find the major companes that will do one way car hire to Brum

Some tips for driving in England (it's not just being on the other side of the road):
https://www.tripadvisor.co.uk/ShowTopic-g186338-i17-k6722631-Driving_in_the_UK_for_Americans-London_England.html

https://www.youtube.com/watch?v=hMQtO6qhkIo

https://www.youtube.com/watch?v=Diu1k_5H45k

Also please read the relevant sections of the Highway Code:
http://www.highwaycodeuk.co.uk/uploads/3/2/9/2/3292309/the-official-highway-code-with-annexes-uk-en-12-04.pdf

The easiest way to get from Portsmouth to The Cotswolds is to take the M27 around Southampton > then M3 towards Winchester - (which is worth a visit) - followed by A34 expressway north - just S of Newbury is Highclere Castle (Downton Abbey). Anyway, the A34 will take you to Oxford (worth seeing - as is Blenheim Palace in this area) but you would then need to take the A40 westbound to Burford to be in The Cotswolds. Routes to the west via Stonehenge and Devizes are non dual highways - for the most part. I suggest you click the link to the map to look at your route options. Zoom down and drag on the yellow man to get street view to see what the roads are like. Look in particular at Winchester and also at important junctions - where you switch routes. If you think that driving is not for you, direct trains go from Portsmouth Harbour to Bath - where you might like to spend a couple of nights. I think that Mad Max has tours of interesting places from Bath - or you could hire a car to drive to the northern Cotswolds. (You would not need a car in Bath - zoom down and look at the streets.). You can get trains from Bath to Birmingham International station = the airport but you must change at Bristol Temple Meads and Birmingham New Street. Most people going to Ireland form Bath would take the short bus ride to nearby Bristol Airport. See www.skyscanner.net
Trains = www.nationalrail.co.uk (Another train route goes Portsmouth Harbour > Southampton (change) and then up to Oxford and Birmingham). Train fares are cheaper if pre-booked about 11 weeks in advance in going on longer trips.
Here is the map - with live traffic flows coloured on the routes:>https://www.google.co.uk/maps/@51.2683279,-1.2568906,9.57z/data=!5m1!1e1

Europcar have an office next to the historic dockyard which, as someone has already mentioned, is well worth a visit. The easiest way to get there is via a short taxi ride (it is walkable from the ferry terminal however if you're carrying luggage you might want to opt for a taxi). From the Europcar location it is a very easy, short drive to the M275 motorway which will take you on to the M27, M3, A34 and eventually the M4 towards the Cotswolds.

Another option is Enterprise car rental who will collect you from the ferry port and take you to the rental location. The drive from there is also relatively easy as you take the Eastern Road which is a dual carriageway leading all the way to the M27.

Unfortunately there are not really many rural areas in the vicinity that have car rental. There is an Enterprise near me in Havant which is located on an industrial estate and is a very easy drive onto the A27/M27 in less than 5 minutes. A taxi there from the ferry port would probably cost around £15. This would be the best option if you wanted to avoid driving out of a city and will get you on to a motorway very quickly where you can take your time adjusting to driving on the left. Unfortunately there isn't an easier way to get to the Cotswolds from Portsmouth, driving is by far the easiest and quickest, it took us just over 1.5 hours last Sunday. The route we took (although we were coming back from Derby via the Cotswolds) was M27, join the M3 after passing Southampton airport, come off at the slip road for the A34. Continue along the A34 and join the M4. This will take you past Swindon and a GPS (very advisable to have one) will direct you to the main towns. You will probably want to hit Bourton on the Water first and then follow the road up through Stow on the Wold and Moreton-in-Marsh.

There's no motorway running straight between Portsmouth and the Cotswolds, but timewise it's about equal because driving on the country lanes you'll have to go much slower,

That's not strictly true. Whilst there is not one single motorway linking the two there is a route that encompasses both dual carriageways and motorways almost to the point of the Cotswolds. It is a far quicker and easier route than taking the country roads.

JC, thank you for the clarification. I've edited my comment to add "single."

I was thinking of the A336 - A348 (what I think of as a country lane) running north to Marlborough, which goes through part of the Savernake Forest and could then connect with the road westward to Avebury and thence another connection northward. It is a lovely drive, IMO, but not fast.

Yes, I've taken the Marlborough route (from Bristol) and it is a nicer drive albeit slower.

We took an American friend to Marlborough and he loved it! It would make a great place to break the journey and just have a stroll round.

We had a bad experience with Europcar, but the have an office next to the Holiday Inn on Herbert Walker next to the cruise port.

We had a bad experience with Europcar, but the have an office next to the Holiday Inn on Herbert Walker next to the cruise port.

The OP will be arriving at Portsmouth ferry port rather than Southampton cruise terminal.