Over the last 12 months I have successfully claimed back PPI on a couple of loans I had taken out (including my mortgage).
It's pretty straightforward, and the only one who was reluctant was my mortgage lender. They replied to my letter, saying that they didn't feel they had done anything wrong. I wrote back, thanking them for their response, but stated that I'd have to take it up with the Financial ombudsman. Within a couple of weeks, the bank then admitted liability and transferred the full amount (plus interest) into my account.
I'm sure people will be tempted to hand over their applications to one of those companies who promise to get it back and then take 20%. Don't do it, it only takes 1, or 2 letters max. If anyone wants a copy of the letter I sent then pm me (I'll only want 5%

).