Well I got a significant amount of my offers well before the deadline (around november?) and I know many other universities hand them out before the deadline. Whether that's because they were sure they would give me the offer anyhow or because they were working on a first come first serve basis I can't say. I would probably still apply early so long as you've thought about it well and have visited the uni's in your AS year because the way I see it is that universities have a limited amount of offers to hand out so in the beginning there may be less competition so you may have an easier time whereas later say if there's only 5 places left and 50 applicants sure they may give you equal consideration but that's in light of the 5 spaces remaining I suppose so they can only pick 5 out of the 50.
I could be wrong though. I'm sure there's a couple of admissions tutors on this forum who would probably clear up any questions you have. Probably changes per uni too because some don't even hand out offers at all until after the deadline).