According to the link in my post above it is compatible with these: Nokia 3100, 3200, 6100, 6220, 6230i, 6610, 6820, 7210, 7250, 7250i,
You can change the cradle for maybe 50euro and leave the rest in place. If you're entitled to an upgrade, select a phone on your phone companies site, then check it on Nokia's site for compatibility with your existing carkit - should tell you what cradle you need.
I actually have same carkit and a phone that does not now fit cradle. You can pull out cable on bottom of cradle and plug directly into phone (if it's a pop port one) to charge it.