Newbie Looking for help please

Under normal operating conditions, the oil warning light should not be coming on at all when the car is being used for normal, everyday driving. It only comes on when the oil pressure falls below the minimum operating pressure allowed for your engine, which I think, is around 5psi in old money.  I drive a Zaffy with exactly the same engine, the 2.0dti and it has almost the same mileage as yours. I did have an occasion about 18 months ago when the red oil light started flickering when the engine was hot and idling, but, after testing the oil pressure switch operation, and finding it working OK,  I changed the oil I was using to 20-50 fully synthetic, which is a wee bit thicker and doesn't thin so easily when it gets warm.  I also thought that the engine was starting to run a little bit hotter than usual, so at the same time I cleaned out the cooling system radiator core, which had got a bit of debris, dust and old leaves stuck to it, by carefully reverse flushing it through the fins, with the garden hose. These two measures together have completely stopped the oil light flashing on warm idle, although I am still getting the odd orange "spanner light" when the engine is warm, which is a quite separate problem that I am still trying to solve.  

You might also check out the operation of your thermostat, which might not be opening quick enough to stop your engine overheating slightly which in turn will thin your oil even more. There is also the possibility that it may have been taken out all together, which would be one reason that your engine takes a while to heat up - the other reason being a problem with your water pump not working properly... Good luck with your investigation.... Cheers.. Robin