On their website is a form produced by the FSA. Fill it in, and send it off.
No need for copies of paperwork or policy numbers - they will find both.
Try to be as specific as possible, and don't mention multiple issues if poss. The more you mention, the more they will think you're trying it on.
The kind salesperson man said that because of my credit history I HAD to take the PPI to get the loan, etc etc.