I think go for Birkbeck, I studied at Surrey and yes it is a nice university but the area is very quiet. You will be in London, the greatest city in the world and have a degree under the University of London banner, which also helps for jobs in foreign countries.
I know a few people who gave up good offers at top universities just to experience London. Birkbeck is also a great university with a more mature community, so you will definitely enjoy it there.