^^ It's not a bad price especially if you can knock the guy down to £4K leaving you a grand to fix up some of the bits (£300-£400 for four alloys refurbed, painted wing £250-£300 odd at a guess) but still if you can stretch to more then I would as you could be, just like Bradders found out, opening yourself up to more expensive bills in the future.
Having said that though if it has a good service history with it then I wouldn't let the mileage put you off necessarily.
Personally I'd rather spend some money on going to see that one in Scotland first. I'd definitely at the least be ringing him up to ask him what service history he has and any more info on the car (like what fuel does he use/tyre condition/clutch changed? etc).