Maybe £2-300 parts and labour to get the failures fixed. I.e Brake hose, CV joint, bit of welding.
A bit more if you get a new wheel(s)
Advisories are not that expensive. Two new top spring plates. Maybe some welding for the seat belt anchorage. They can't check the sills because of the plastic sill trim (good or bad that's your call)
1. Is this the first Mk2 you've seen?
2. What's your budget?
You can probably knock quite a bit of the sub £600 price when you factor in the work needed to pass the MOT.
AS EVER... the golden rule...Buy on Bodywork.
If the body is fine (or easily rectified cheaply or easily) then it comes down to point 2.
Any pics? Year, Mileage etc.. Service history. The usual.
Me.. If the bodywork was good (No rust) then About £400 sounds good for an MOT failure.