Glad you got a refund, obviously the seller was a decent guy and maybe thought if someone bought it cheap they would try and sort the issue out.
Thing is you don’t know who has been trying to sort it previously, it just looks like someone’s been throwing parts at it hoping something would work.
What I’ve learned over 6 years of ownership is that these motors throw up all sorts of spurious fault codes that may not actually relate at all to the actual issue and only technicians with previous experiences with the faults can see through the imposters.
If you want a good R then I’m afraid your going to probably have to step up and pay a little more than 10K and probably have to travel far and wide to find that perfect car.
Good luck keep us up to speed with how you get on