I shouldn't worry but unless your son looks like the picture below then he wouldn't get a look in at the Freshers' Fair UAS Stand in my experience. This is probably why so few end up actually joining the RAF at the end of their UAS time - although a few do get married to the Boss and the QFIs...
PS. My experience of UAS in the 80s/90s was that very few ended up at the top end of their flying training courses. It made me question why we bothered we UAS. However, having now read the line about it being Trenchard's plan in giving RAF experience to the great and good who wouldn't join the military but would go on to be politicians, financial gurus, businessmen, doctors, etc...