whats the problem - they were well above legal requirements, the tyres have done another 5k - so they can't have been to bad, you just don't change tyres for the fun of it, you should have spotted this at the time & if you were concerned about them you could have haggled a bit during the negotiations, i suppose you had to put fuel in it as well, i can't see a problem with that - whoever you buy from - i just sold a car with a tyre that was getting low & pointed it out to the buyer & it had passed an MOT the day before. mind you it was only a £3k car!
you live & learn.