You can generally only take our either PCP or HP at the point of purchase, you can’t do it after the fact, so I doubt you’lol be bale to convert PCP to HP.
HP used to be interesting because it was secured against the car which meant you could borrow much more money at a supposedly attractive rate, however the amount you can now borrow as an unsecured personal loan and the low rates that are available make HP look like a silly idea. The other advantage of a personal loan vs HP is that you will own the car. With HP you don’t legally have title to the car until the final payment is made.
Speak to the lender for the PCP and ask for a settlement figure, then look around for a suitable personal loan.