I sold my '62 plate 30k miles Mk6 GTI last September to a member on here - sold it for £15,500. My original price would've been 15,900 but I took £400 off to account for it needing all 4 diamond cut wheels refurbing.

It was a 5 door Dsg with leather, Dynaudio, 19" Glendales, ACC, RCD510. It didn't have any Nav or parking sensors.
I didn't actually get as far as advertising it. I had 2 people interested, someone who came on the forum specifically looking for a mk6 and someone who was already a member. It went to the latter.
I guess I could have advertised it and probably got a bit more but the buyer was right, the timing was perfect (month before my R arrived) and didn't have to endure tyre kickers and time wasters - so went for it. Add to that I got 12.5% (over £4,500) discount off my new R order via Drivethedeal, and my overall cost to change was very good.