Firstly, a repayment term of 5 years on a £100k loan plus interest is going to be over £20k per year, you'd have very little left to live on even if you got into somewhere like BA or easyJet. Starting as a turboprop FO would be nigh on impossible. Bear in mind that those who do the integrated schemes often have a repayment holiday for a couple of years (you can't pay it back until you are earning), that would likely add at least £10k in interest before you start repayments.
The TUI cadet scheme is currently open, BA and Aer Lingus are also likely this year. If you can apply for all three, plus any others which come up, I'd recommend doing so.
Regarding getting another trade first, the airline industry being dependent on discretionary spending has economic highs and lows greater than the wider economy. It would be useful for you to learn a trade which you can revert back to if you can't get a job after qualifying or if you are made redundant whilst flying. It would also give you more to talk about at interview.
Lastly, have a thorough check of the medical requirements and don't begin PPL training without at least a Class 2 and CPL/ATPL training without a Class 1. Some recommend getting a Class 1 from the start.