We are in a time of flux at the moment with used car prices and over the next couple of years this isn't going to get much better.
Using the market over the past couple of years as a guide, you are probably not far off the mark with the value of around £5k, on the assumption the car still in the same sort of condition and the service history is kept up.
However, if diesel prices continue at the current level or rise, then people may re-consider their options. Certainly I know several company car drivers that have taken the option of a 318i petrol over the diesel counterpart because of the costs involved.
Ultimately though if you enjoy the car, don't worry about it. You could have done a lot worse.
Read my motoring and car related diatribe at.........
http://TegTypeR.blog.co.uk
Updated: 16th November 2008