£650 a month is completely bonkers - that means that your training will cost £85,000 at todays price!! Which, if I've got my sums right, is about double what it could have cost you. Not only that, it would be more than half your take-home pay as a turbo-prop F/O!! You couldn't even think about being an instrcutor for a couple of years.
This lark seems about making choices to give you options. That route closes most of them.
It's a mill-stone that I am quite sure you will be regretting five years in. And you'd still be thinking, 'only another six years to pay it off'
