You don't need to go through the
fos
but if you have then a finding in your favour may save you some work when bringing a court claim.
However, you would have to have clear evidence of mis selling. This means that you would have to have written evidence that they knew of your unemployment or disability etc or other reason why PPI did not apply to you.
Alternatively you would have to have clear written evidence that they did tell you that PPI was essential to get the loan etc.
In other words you must be able to prove in court that there was some misrepresentation which caused you to buy the policy and to part with your money.
The more glaring the mis-selling then the easier it would be to get restitutionary damages.
For instance, if you could show that a form had been altered, then this would be fraudulent. Not only would you almost definitely get restitutionary damages, but I expect that you would get punitive damages as well.
Punitive damages is an extra award on top which demonstrates the displeasure of the court.