Walking from Stockwell to Brixton at 2am on your own isn't fun to say the least.
Don't agree with the "for people tired of the city". Some people just don't like living in cities full stop, depends on tons of things. I've been to St Albans a few times, and it has an alright nightlife itself, not to mention there's nothing stopping you going out in London if that's your thing, just a little pricier for transport. Going out in London costs a bomb anyway. I've paid £10 for a JD and coke on numerous occasions. The student nights are a bit cheaper, but still very expensive compared with other towns/cities.