Martin
I have the same problem.
Mine is starting to have some major problems, but i have been told that they no longer make them and the replacement is some crappy thing (not Nokia)
Usually I just ring and get a new one delivered the next morning, but now I will have to wait for the engineer to fit a new car kit (assuming they do one for this new phone) and then learn how to use to non Nokia pants phone!
I even considered getting myself a new different Nokia and using the Sim, but they cannot just replace the craddle in the car kit, it has to be the whole thing and if i do it off my own back i have to pay and I am too tight for that.
If you do find a supplier would be interested in details as well.