Mines just crept up to 55K now

You need to go over these motors with a fine tooth comb mate.
I wont post all the same as above as they are good suggestions, also checkthe sunroof, open it right out (check for any falling flakes of rust, which will be a bad sign), if the runners look mine like mine did should be good.
Rear chassis rails, rear sills up behind the kit, common place to go as with behindthe back bumper at the sides, my last S2 had gone right through here, although not an mot failure so not too much of a worry.
Just spend as much time as you can, if it takes an hour to look over first off even before starting the car then so be it.