HelpHound

Waterstone's Gower Street is the largest academic Waterstone's in the country.

It's about 4 floors - the ground floor has contemporary novels and the like, gift cards and notebooks and wrapping paper and such, but go up or down and it's pretty much the source for any university student. They carry a wide range of textbooks for almost every subject - Law to Engineering, Medicine to Mathematics - and can order books they don't have in stock for you.

The staff are helpful and are willing to locate books for you if you can't find them without a fuss.

Also, you can get a student discount card at Waterstone's which of course, helps with the cost.