Looking into what is going on at BA and other major airlines in Britain regarding T&Cs, I certainly wouldn't be paying £100k for training. There's likely (in Europe at least) going to be a decline in T&Cs for the foreseeable future as airlines take advantage of a pilot employment market that is in their favour. If the OP's son has an EU passport/European language skills, I'd be tempted to get a backup career outside of aviation and keep an eye out for any sponsored programmes (though it's likely these will be years away). As things stand, I'd only consider a move into flying if an airline paid for my training, there's too much risk of unemployment/dire T&Cs at the moment.
I wouldn't go further than a PPL at the moment, it's fairly flexible in that it'll provide an idea of aptitude and give the OPs son an idea of whether or not he enjoys flying.
In the meantime, take a look at getting involved in various aviation organisations such as HCAP and the Air League, networking is important in the industry.
Lastly, don't pay large sums of money up front for flight training.