CTC have a very stringent selection process, and I wouldn't get my hopes up about being successful in getting a place with them (that's not to say don't give up before the fight, by all means go for it, and that applies to everything). OAT is the most expensive FTO, and therefore is financially riskier. But they do include a JOC in their course, something which most schools do not.
Jobs are tough to get. It really depends on the state of the industry when you are qualified. You could be the best pilot in the world and unable to get a job.
Being good at the bookwork will be an good advantage for the writtens. BTW "My GCSE results were fantastic" sounds a bit cocky. People who weren't the best at school can and will do just as well as long as they put in the hard work. Any successful pilot has worked hard to succeed in training and get a job.
Getting into €100k debt at the age of 18/19 isn't commitment. It is taking a huge risk and foolish if you don't realise it. People can train for a fATPL at a much lower cost and risk, but they are as committed/determined as anyone else, and will have a lot less to pay back when they get jobs.
From the sound of your post, you seriously need to research this career, and consider all possible training options. Also, there are a lot of university courses that offer pilot studies along with a respectable degree, and there are opportunities to join University Air Squadrons. No school can guarantee you will get a job, no matter how much money you spend.