Nottingham UK: cheap but with strong uni nearby so interesting people to meet or study with.
FWIW I'd recommend other places over Nottingham, though. Birmingham is a vibrant "second city", with low prices and good connections to London. Several decent universities. Manchester is cheaper still. Southampton is cheaper than London and has good culture and a good university. Glasgow is a cheap and rapidly rejuvenating city.
Nottingham is IMO pretty dull. Maybe the parent commenter has better experiences though.