Mine is being part exed this weekend, got £13000 for it, its booking at £13500 so the Mini dealer said if immaculate, but needs a couple of wheels doing and some minor body wear.
Mine is an 09 plate GTI 35000miles, candy white, 18" monza's, RCD510 and leather. So not a bad spec, but by no means the best out there. I was quite pleased with the part ex price. I tried to sell private a couple of months back started at £15500, but just kept getting silly offers so withdrew the ad.
I dont think used prices have been hit to bad in the last quarter of 2012, as i got offered £13000 in Oct from a dealer. MK5 prices have held up really well also, so dont think the MK7 coming out will make to much difference on MK6 values