first thig to do, if the oil pressure switch looks fubar is to change both the o.3 and 1.8... one on the oil cooler and one on the side of the head... not 100% sure which is which... think the 0.3 is the one on the oil cooler, but only use VAG ones as gsf and eurocrap parts are rubbish.
then if that doesnt solve the problem, next thing to do is have a pressure check from a garage, you'll have to ring around cos not all garages have the equipment to do so.
if the pressure is low, then i'd suggest dropping the sump, checking the pick-up on the oil pump for crap(usually the problem) and if so clean it, if not, replace the oil pump with one from eurocrapparts(cheaper than the one in VAG - might not last 16eyars, but will last long enough) then put it all back together with noew bolts and gasket(available from VAG) and then fire her u and see if thhat cures it...
if not, then start crying and worry like mad cos your car is not a happy bunny.
hope that helps
rob