UK - Porsche approved vs indy with warranty

I'm looking to get a porsche (still deciding on the model as I'm a fan of the taycan, cayenne, and panamera). I'm aware of the potential high maintenance costs so the porsche warranty is of utmost importance for me.

I've seen porsche approved comes with the porsche warranty and you pay a premium for this vs indys. However, porsche state you can buy a warranty on any porsche so long as it passes their 111 point test.

Does anyone have experience with buying from an indy, or maybe even a private seller - But taking it to porsche with the agreement of the seller and getting it tested for the purposes of getting the porsche warranty?

I've seen cars being sold by indys and private sellers that have the spec I want but they're very rare to come up from porsche themselves (and much more expensive). Is it viable to get the warranty added on? Is this exactly the same warranty that porsche offer on their CPO/approved used?