Oh goodness. I'm really not going to be helpful in the slightest. I've already overflowed my current bookshelf in the space of three months, and this doesn't count the (literal) walls of books I've left in both my parents' houses. I'm an addict. I admit to it. In my nine months in Cambridge, I acquired about 90 books in my tiny single room, not counting the ones I brought with me in the first place...

Shelves are good. I don't know if anyone in the UK carries collapsible bookshelves, but I've got five of them and they are absolutely wonderful. Of course, if you've got minimal wall space, you could also try tables with shelves underneath, or possibly hanging shelves so they aren't actually showing up on the floor and the wall; just up high.