Ok, I've managed to totally reinstall the server but I'm having trouble connecting the old handsets.

I've done the Enterprise Activation which seems to have worked in that the BES box has received the activation email back and the user's status is now "Running" but then it starts going wrong.

Immediately after activation, I got an error on the handset saying the IT policy couldn't be accepted/applied. I tried sending it again from the server but got no message at all on the handset that time, either positive or negative. The handset isn't synchronising at all with the server.

How can I reset the handset to wipe all existing emails and start synchronising with the new server? I don't want to totally reset the unit as I can't afford to wipe other settings and text messages and so forth.

Any help appreciated.

You can backup using Desktop manager. Wipe the HH and re-activate it and then restore...