If a seller is to supply warranty, one would expect the problems to be repaired before someone looks over the car. That might sell the car a lot easier. You have to repair it anyway because of the warranty.

Only 3 months warranty seems short to me, but I don't live in the UK. Worth checking what the time-length of the average warranty is.

Take great care here. I would do a code read for all systems and an exhaust gas analysis - in my presence - before deciding if I would want to buy the car.
I have seen ABS lamps connected to the oil pressure switch and those kind of things.