Looks like i'm going to get a 2:ii, baring in mind that my sciences degree is relatively difficult, how likely would it be that i find a PhD?
ps that's not to say i'm being snobby about other institutions

A 2ii from oxbridge is still a 2ii, I doubt that your course was any more difficult than any other red brick uni. What I'm trying to say is that you will be up against students from other uni's with a 2i/1st, which I doubt the oxbridge bit will make up for. It won't hurt to apply, but I'd get a back up of a masters the strenghthen you application if you're not successful.

If you're just about to enter your final year then you've got time to apply for a few PhD positions before you need to commit to doing a masters. Your best bet would be to work very hard next year and get your grade up to a 2i. If you are finding you first degree difficult then you may need to think seriously about whether a PhD is the right move for you. Without research experience or an MSc/MRes it is unlikely that supervisors will consider a candidate with a 2ii. Oxbridge will make little or no difference.