Wait, scratch that last post. It's possible I've fucked up and lead you astray on that one with regards to deferral (it's been two years since I did it), so disregard what I said about contacting the Student Centre. Read this one, though I cannot guarantee that is is correct.
However, pay attention to this next part (my memory's a bit fuzzy so I can can only give you an either/or scenario here): You CANNOT defer some SRAS courses. Look very carefully as to which courses can and cannot be put off because it is possible that yours will be one of these! If this is the case, you may (and this is where it gets iffy) be able to reject the offer and simply reapply to the same course (mix your preferences up, save them and then do it again just in case) and try for a late-round offer, but there is no guarantee you will get it second time around.
Because you've only just been given your places (SRAS is only a guaranteed offer, not a guaranteed place; you still have to accept it to get the place), you'll need to reply as soon as you possibly can. You should include with this a letter detailing your reasons as to why you wich to defer until 2008. UNE is usually very quick to get back to you on this.