Have you seen this thread? Fair few pics of what splitters have been used previously http://micra.org.uk/threads/k11-sideskirts-lips-spoilers-splitters-thread.52848/ ..might want to use a different one that you know fits with relatively little/no modification
Mk4 polo front splitter is in the list shown there, I don't know how different the Mk3's were though.. so still couldnt say if it'd fit like