Wow, thank you all for the numerous and quick replies. They have provided a lot to think about and I will now go through and address some of the open questions.
But still, they should have had 2+ years to research and get used to the idea before starting the application. Getting through the hoops is no mean thing...
True, I have done a lot of research and spoken to many people about this. But I during this time I was also at university and I was still in the process of getting through all the hoops. I graduated, and at some point along the way I had also jumped through all these hoops to be selected, and now with the future ahead of me and an offer in hand I am evaluating whether it's actually for me.
SWP, the questions you asked give an insightful answer. I did feel happy when I passed, but perhaps not to the extent that some people who had made it their one and only goal in life might have. Similarly, I went to university because I am interested in the subject (natural sciences), and because this could lead to a range of careers, one of which might be some form of flying. Joining the UAS then put the RAF option on the table. If I do change tack now, and I'm not trying to be arrogant, I think there is a lot I could do. What I would probably do instead is start a PhD (very different, I know).
Regarding isolated bases, my aversion, I think, stems from being cut off from the outside world, or the nice bits of it at least! I believe living in a pleasant area could have a real effect on happiness in life. For some reason, neither the bases I have been to nor their nearby cities live up to the standard of a nice little university city some 50 miles north of London. Yet this is, of course, a bigoted view and does not take into account beautiful Welsh valleys or Scottish highlands which surround some bases.
IOT, I can get through by playing the game when necessary and just getting on with it. But it will make me question why I am doing it all, especially when I'm not entirely convinced by the life afterwards.
Once again, thank you for all your input and I am still to make a final decision. Once I do, I will let you know.