Something odd going on there.. why would the owner not spring for 2 new tyres? 12 months MOT always gives a new buyer confidence and 2 tyres are a small proportion of the car's worth, especially if the seller wants to get top dollar for it (and don't we all, when selling a car?). You could even put "budgets" on to get it through the test.
Fishy..
Cheers,
Gaz