You ask how to pay it back (I'm ignoring the other comments in this thread as they don't help me help you)?
I don't mind how you would pay it back. Cash in the post. Postal Orders delivered by pigeon. Coins via a duck. I don't mind.
All we would need to do it work out a repayment schedule. Obviously it wouldn't be a legally binding thing, so if you defaulted on the payments I would just be out of pocket and a bit annoyed. Hopefully you wouldn't do this by arranging a sensible payment schedule.
So, could we say 5 pounds a month, cash in post? Or is that too much/too little?
Another thought - can you part exchange some old Playstation games in your local games shop? You might get cash, but more likely you'd get vouchers. I would be quite happy to exchange it for vouchers, as long as it's a common shop, like Game or PC World.
You tell me what you can do (via PM if you don't want everyone to know), and I'm sure we can work something out. But you've got to tell me what you can afford to repay, when and how.
Edit: It turns out some of the above posts do help - this splitting a licence idea mmight just work. But either way we need to know a bit more from you.