Hmm. Seems to be some confusion going on as to what happens when you top up the oil.. just to clear things up, when you pour oil in through the filler in the rocker cover, it doesn't just sit in the cylinder head, it drains straight down through the engine into the sump at the bottom.. you're not going to see it filling up unless you've -seriously- overfilled it..
When you're filling the oil, always check the dipstick to see how much is there to start with. I think polos take 1 litre between minimum and maximum marks (someone correct me if I'm wrong..), much more than this and you're risking damage.
One thing I've found, last time I overfilled my oil, it just sprang a head gasket leak. Not compression or water, just the oil seal - started dripping out from where the engine number is stamped, over the alternator. This may well have happened, if it has, personally I'd count your lucky stars because it's not a big job to change a head gasket on a polo and it means you've (hopefully..) avoided any more serious damage...
