I believe that the information given by the second 'informant' is incorrect.
Unless policy has changed in the last few months, both the RAF and the RN allow most applicants 2 bites at the FAT cherry so long as the applicant is under 21 when they first take the FATs. I am not sure, as A_A agrees, if the attempt that your lad has already made should be classed as a 'first' attempt, IMHO it shouldn't be. However it may well be counted. Regardless, policy has generally been that if you take the FATs at a pre-university age and don't do so well it should not preclude you from taking them again at a later date. This system is obviously BASED on pre/post university 'brain development', however if your lad does not go to university that should not preclude him from attempting the FATs again after his first attempt.
As a slight aside/ extra info, I understand the RN is now recruiting "Aircrew" not pilots and observers so although in the past any wannabe pilot had to pass the FATs on both pilot and observer skills, now you need a GOOD pass at both on the basis that you could be streamed into either job once you have done grading for both once you are at BRNC Dartmouth....
Oh, and slang or not, it is def Sleaford Tech. Still, its got the best cinema around. Oh sorry, I mean Flicks