Got it sorted, thanks.
I was getting confused between the passkey and the passcode, and there actually is an option to change the passkey. I set that to 0000 and the phone connected without a problem.
Still seems strange though that the phone tries to connect without asking me to enter a code number, maybe this is because the MMCS is recognised by the phone as a 'headset' for Bluetooth purposes ?
Anyway, having got my phone connected, next step is to have a go at getting the Remote Control app working !!!