Please please dont get Mum and Dad in Debt!
My advice would be to continue with your PPL. Get a normal job, and enroll on a Distance learning course for the ATPLS with Bristol Ground School. The cost of this is just south of £3000 including exam fees. Distance learning courses can also be done at BCFT in Bournemouth, Cabair and also London Met.
So what you need is : PPL, ATPL exams, 90 hours hoursbuilding considering you will have 10 solo hours already done from your PPL training. Then it's the CPL IR. After that its either an MCC or a flight instructor rating.
The question is how do you achieve this without plunging you or your parents into copious amounts of debt with as you said extortionate interest rates?
You need a couple of things on side from experience.
First is time. You are a young guy/gal and have plenty of time to do this, trust me you REALLY do.
Second is patience, it will take longer than the integrated route but the risks are less and the financial burden is much much less.
Get your PPL done, get a job, do the exams distance learning while still working at your job(it can be done). Then get yourself a couple of weeks off when you have the money SAVED for your hoursbuilding and go and rent the cheapest aircraft in America and do your hoursbuilding. You now have to do the CPL and IR. You can do the CPL in America and come back to the UK to do the IR. I am confident you can get the CPL and IR for 15 to 16k.
You will find that this is a long way off the 50k straight up with huge crippling interest rates.
Just be patient and try to pay for each stage as you go if you can. It will take time but as I said you have plenty of that.
I hope this helps.