Have you done a tax return for 2011 - 2012? You can claim tax back on that year any time now, once you have your P60.
We always advise to keep receipts - saves any hassle should HMRC decide to check a claim, which they are perfectly entitled to do, and do! Doesn't matter how you keep them, in a box, in 12 envelopes, but yes keep anything to prove the claim, should you need to.
There is no definitive list of what can be claimed for as each person's claim is unique to them.
Expenses you spend to do your job can be considered. The way we work is that we will do a return, with you, to include all your relevant expenses, which is where we differ from many competitors - they concentrate on travel/ mileage only.
If you would like us to work with you, scaff1989, just give us a call. Sorry I can't be more specific, but as I say, all returns are unique to each claimant.