Don't be too put off by the market. I qualified at a terrible time, the downturn hit just after I finished my IR, and I knew many of those going through training and qualifying into the continuing bad times after. Everyone I know who persisted eventually got a flying job, almost all have survived the current downturn, although many are flying less. Your son is young, he has plenty of time to pay his father back in cheap flights and in treating you well in your (distant I hope) dotage. Being young he will also find the flying training easier.
Personally I would suggest he seriously considers not going to university if he is really serious about the flying, unless he really wants to study. He might be better off trying to find work in the aviation business, even if it would be menial, while completing his courses. In that way he does not accrue even more debts, can earn some money, makes contacts if he is in an airline (or even in some flying schools where airline pilots fly for fun) and if he works at a flying school for example will benefit from the conversation, the (admittedly sometimes dubious) advice and from cheap flying.
If he finishes and really can't find a job, then he can consider a degree.
£80,000 is an integrated course. A modular course is much cheaper.
After PPL he needs to build up hours until he has 150 and complete the ATPL exams. Within that 150 hours he must have 100 hours as pilot-in-command (PIC), and once he has 70 hours PIC he should do a multi-engine rating. If he is bright he can do the groundschool on a distance-learning course. With 150 hours and ATPL exams he can do the CPL and the IR (actually he can do the IR earlier, and the CPL after the IR which can be slightly cheaper if he is really good). He will need 200 hours to hold a CPL, but he should have that by then (minimum I heard of for this route was 205 hours, and I gave him a job, he was a great pilot - he was about your son's age when he started, 20 when I signed him off to line flying).