Thought it might be of interest for some of you, unfortunately I don't have the money at the moment or I would be in the bidding war!
Genuine GP Skirts on eBay UK (in Doncaster). Current bid is £215 with 9 days left. There have been 6 bids so far, I'm sure these will go for a lot more than that though due to how rare they are! I'd guess about £360-£400, but that's based on nothing! BMW MINI COOPER S GP R53 JCW R56 SIDE SKIRT AERO SILL JOHN COOPER WORKS COUPE | eBay