Just because you haven't signed anything an implied contract still exists...however it depends what you agreed on and if there is any terms of reference which relates to refunds. I would have a look....
If i was cabair..(which i'm not) i would do the gentlemanly thing and refund even as a matter of goodwill (seen as they make a fortune already in hidden charges) as it limits his career chances.
My advice is...if speaking to them dosen't help (and you've looked at the terms of contract) then seek a solicitors letter and take it from there.
The moral of the story is never pay up front especially if you think you may fall on hard times.
P.S. £8900 seems a heck of a lot for a PPL (money grabbing b*stards)