Nobody has ever been entitled to receive compensation simply because they took out PPI. They are (or, more accurately now in most cases, 'were') only entitled to receive compensation if they'd been wrongly advised to take it out. (e.g. if they were self-employed and the person promoting the product omitted to tell them that the weren't covered for loss of employment).
So any compensation that might have been due would have to come from the firm employing the salesperson (who was undoubtedly seeking to maximise his/her commission) and not directly from the firm actually providing the PPI.
So it would have been the dealership who were responsible for compensating you (if you could actually show that the PPI had been mis-sold). If that firm is still in existence (even under a different name or as part of a larger concern) you can no longer submit a valid PPI claim as the deadline for doing so has now passed.
However if the firm has gone bust (so that you couldn't/can't claim directly against them) you can still seek compensation from the Financial Services Compensation Scheme. (The PPI deadline doesn't apply to such claims). If they went bust before 1 January 2010 you're entitled to 100% of what you paid them up to a limit of £2000 and then 90% of anything else. If they went bust at a later date you're entitled to 90% of your claim.
Relevant links:
https://forums.moneysavingexpert.com/showthread.php?t=2142913
and
https://www.fscs.org.uk/what-we-cover/