Sorry to hear that mate :( I guess it explains why he never listed the car here For Sale but I thought he was maybe just trying to bow out without making a fuss. And I agree I hate people that think it is ok to sell a car like that with known issues makes me mad well lets hope karma returns the favour, mind you more likely just rip some other poor genuine buyer off
But like you have said at least you have taken the steps to have it sorted and after it's done will have a car you know is working.
And I can tell you now driving 1 hour will not blow the head gasket, and lets face it, it should have been warmed up before he boosted it on your test drive.