bad points for rust ?
My experience for the body...
inner front wings (ABS might be mounted to nothing!) , battery tray, behind and below the headlamps, front foot wells, all sills inner/outer extending into the floor pans, A post, B post, open 2nd row doors and rust on the arch , boot pan, seals around the rear skylight windows. Feel passenger footwell carpet to check for wetness - might be rust hole and road water coming but also might be leaking coolant from cabin heater which is a major pig to replace and can nuke the engine when coolant runs low. Take a screwdriver and ask if you can removed trim and lift the boot carpet.
Chassis should be spotless and corrosion free.
r reg probably got tired suspension so look for saggy springs and worn bushes and clonking on the A-frame ball joint.
on a tdi...
See if the injection pump has had the antitamper cap has been removed to see if it been fiddled with.
See if the EGR has been blanked or not.
Important to know when timing belt was done.
if it's like an ES model then check all the leccy bits and see what works - defo nice to have the seat functions fully working, all leccy window wind mech's working - esp check rear door one go both down and up again