Hmmn long time since I went through exactly what you are doing. I joined in 92, was initially accepted for pilot training, but was then sent a letter informing me that due to cutbacks they could no longer offer me aircrew, if I wanted to still join I could as Admin Sec, but If I didn't want that I had to wait a year and try again, with no guarantees of acceptance.
I elected to join then, and try for branch change. On my IOT there were 3 other guys who had the same offer. 2 of them had told the RAF that it was pilot or nothing and they would wait and try again in a year, the other had done as I had. The 2 that said they would wait were then sent another letter offering them GD/P. It appears the RAF wanted those that had the aptitude and also the determination to be a GD/P and not the determination to accept something else (as I did).
Anyway as luck would have it my first admin posting was to RAF Valley. I had a great time, spent some 50+ hours in the back of hawks, and as I was the Flg trg Wg Adjt I spent all mytime with the CO and Chief Instructor. They both wrote on my behalf specially recommending that I be considered for branch transfer to GD/P. So with the Stn Cdr and the Chief Instructor of the RAF's fast Jet Training School both saying I had what it took, of course you know there could be no other outcome...you're right the RAF said poke off and stay a bluntie you loser (or words to that effect). Every year I applied for branch transfer and every year they said no until I was 29 and then they said 'you are now too old to be a pilot stop bothering us'. So I resigned, borrowed shed loads of dosh, got my commercial licences and now fly 737's for easyjet.
Maybe the above will give you an inkling of how things might work.
Regards and best of luck.
BlueJet
Flt Lt (retd)