J plates dont tend to rust that bad tbh
Body :-
Rear arches as already said, £ Circa 500-700 to put right (if you want a good job)
Floor:- Tends to be passenger side caused by leaky heater matrix. But worth checked out sills too, (9 times out of ten the inner sills need attention too)
Front wings are plastic, but the inner wings are susceptible too
Enginewise, the hydraulic tappets in the F7's are LOUD with age, but a good oil will sort them out.. if not you can buy a set of 16 on ebay for £65ish (better than the £300 from renault)
Steering column's are also prone to ware causing ALOT of play, check for this. (canbe fixed with a welder)
Some power steering pumps tend to be LOUD but these can be swapped out (Mat Brown is your man for a spare)
Gearboxes tend to be weak but there are lots of options for replacement. 172 cup, Williams, Megane etc JB3/Jc5 series with speedo drive.
if you need anyhing let me know