you were more than lucky,in the current market place that is a totally unreal p/x value,but well done.
The car books at £4750@60k Cap Clean & £5575@70k Glass's Guide there suggested retail is £8125 and £8025.
I am selling a 55 plate wagon with ppp for £9995 with half that mileage.
Unfortunately the market conditions dictate values,everything is relative,if new car prices are falling then p/ex values will also be driven down.
Gav