Try http://www.fordpartsuk.com/ and request the parts you want with the best description if you don't know the part numbers.They won't have the parts on the actual website,but they put themselves out to find what you want.They search stocks at other dealers all over Europe.

Me and a mate are restoring S1's,just a few months ago they got my mate a brand new rear bumper with end caps already painted,back panel,complete tailgate and even interior rear arch trims! and prices weren't bad either.These came from Germany.

We find that the dealers can't be bothered to look up the parts any more and even if they have them they're not logged on their databases.