FEAR NOT.
In my experience people quite often don't have the recommended text. You won't get penalised for having a different one and it doesn't take long to find the right page even if you do have a different edition. In some cases even the recommended texts aren't the best ones to have: we were reading an Oscar Wilde play in the first year and those of us who had the recommended text really struggled to write our essays as there were no line numbers given, and it's really annoying and somewhat unprofessional to have to commentate on a play when all you have is the page number and the act number. So when book shopping, try and get the recommended editions where possible, but don't worry if you have a different one and definitely use your common sense.
Amazon Marketplace and charity shops are most definitely your friends here. I would advise you to avoid the uni Blackwell's like the plague as it's hideously expensive. I only used it in emergencies. When using the library, organise yourself and be prepared - try and get the background reading a few weeks in advance and extract relevant material. You may end up spending a lot of time making notes, or a lot of money on photocopying, but it's definitely less money than you'd spend on buying the books themselves.
As for the reference books on the list, don't buy any until you get there. Many of them will only be used once and material can be photocopied from library books. The ones that will be used more often will become apparent when you arrive (the Rivkin and Ryan book that you use for C&C is a staple though, so definitely buy that!).