I have nothing to do with
GAPAN but I believe they do aptitude tests. They have no hidden agenda and probably can offer advice. They do have small sponsorships too.
Ian, unless you are prepared to write off the best part of £100,000 then I would encourage your son to learn in modular stages.
Yes, sadly, modular is seen by some airlines as "2nd rate" it's the same licence.
What I would definitely encourage him to do is get any sort of job and save. I know, a strange concept in this day and age but it will focus his mind and keep him keen. He'll be able to train consistently with minimal breaks if he has some cash behind him.
I gather he's medically ok? Not colour blind or diabetic?
If he has the desire and ability, the military is one option.