I had a similar predicament last year. I had all of my offers from Uni and was told by the RN that I definately would not be going to selection until the end of the year. As it happens, I am going to Portsmouth beginning of next year.
Therefore I had to think to myself what to do. I knew straight without really thinking too hard, that I wanted to go Military Aircrew before Uni. So phoned the Universities and asked to defer me a year. They were fine, and I now have a gauranteed place next september in Uni.
My point is - there is no point in going to Uni if you will have to leave after 3 - 6 months. Personally I'd have a gap year (if it comes to that), finish selection in that year, and go on from there.