For population density, anywhere south, or east, of Birmingham - there are a lot of flight schools, and by and large flying schools in Britain are pretty good with enthusiastic instructors.
Bournemouth is a pleasant city, with a large airport with some flying training going on - but according to a friend of mine who rents an aeroplane out there, extremely quiet at the moment. Your best bet is probably around London, where there's plenty of non-aviation work, plenty of people to talk to to improve your English (with a dialect and accent that'll be universally understandable in an aviation context), and a lot of flying schools where you can look for work within an hour of the edge of London, so easy to travel for interviews and the like.
See if you can get hold of a copy of this month's "Flyer" magazine - it contains their UK "learn to fly guide", which will give you a good idea of where all the main schools are. Have a look at
SkyDemon Light as well, which will help you find your way around UK airspace and airfields without having to spend any money yet.
It's only fair to say that there are a surplus of native English speaking flying instructors in the UK, so your English will have to be excellent, and your skills extremely good to beat them to the jobs that are available. There's also a bit of a suspicion of the quality of instructors qualifications gained overseas, that will give you problems.
G