Its been a while since I’ve done a hpi but you could get them instantly. Ideal if you have a n iPhone. Think tyre also cheaper now if you want to do it just in case.
Aa checks are fine But they tend to only point out the bad bits. Do you have a mechanic mate? I used to take a mate until I learnt a thing or two and I take a jack which I would use for inspections if I couldn’t see from generic positions. Look at all the records, services etc as you would in a dealer.
Take money with you but leave some with your mate so you not just pulling out 4k for a 4k car.
What car are you looking at? Do you know the typical problems associated with it and would you be able to spot them?
An hour and a half isn’t far to go. My met who loves his car has been known to drive for 4 hours although he bought a dodge charger which died 1 hour into the journey.
Don’t forget if you do pick up the car that day make sure you can insure it there and then with your insurers