just look out for the normal punto faults really, old cam belt, blown head gasket, worn clutch/gearbox, power steering. all can be costly.
being a 16v, if the cam belt snaps, game over as its an interference engine, if it snaps, pistons will mangle the valves etc so u wanna be checking for the last cam belt change in the history, if no records, budget for ~ an additional £300 to get that changed with a new water pump etc. test drive the car and check for signs of over heating, if it goes above the 1/2 way mark on the temp gauge on a "normal" run, walk away as it may mean the HG has gone, but as a precaution, check the oil filler cap/dipstick for "mayonnaise" and the coolant level/colour, if its low or looks brown, again,id prob walk away. when changing gears, the clutch should feel smooth and even as u press the pedal and there should be no noises and a smooth gear shift. steering should be easy as well, avoid if it feels heavy or there are any warning lights to do with the PAS - but also be aware that a weak battery can also cause problems with the PAS so check for the age of the battery, just keep in mind that if u need to change the column, its gunna be costly. any warning lights on the dash should be a concern so question them if there are any, also note what lights show up when u start her as they may have taken the LEDs out to hide faults. in particular, the engine management light, steering, abs and airbags.
check the usual suspects for signs of rust as well, its a galvanized shell so rust under the sills, roof sills, arches etc isnt a good sign.