Eina! Thats £4600 for a GTV with 60 odd thousand miles on the clock. I paid £2.4k for mine last year and now its probably worth around £1.5k. However the fact that the cars are more expensive in SA means you are more likely to find a peach as the GTV still hasnt replaced the Nissan 1400 bakkie as the windgats mode of transport!
First off try for FSH.
Also find out if the car has had a new timing belt. If not get it done NOW. She should have a new one very 36k or 3 years IIRC.
Secondly listen to the rear suspension if it is clonky you may well need to replace the bushes. If it isnt too late that is - otherwise you can start digging around in scrapyards for a rear subframe.
Check the tyres for excessive inner wear. This can point to your wishbones being knackered.
Check all the electrics work and that you dont have any warning lights.
Check oil level. Oil level is critical on a TS. Low oil can point to the car not being looked after.
Rust shouldnt be an issue even living down in Plett but check for it anyway - it could point to a lousy panel beating job.
There are loads more things to look for - I am sure you will have plenty more things added to this list.