Ok, I have just spoken to the company that makes the webmail software and they say that it would be VERY easy to acheive this.
All that would need doing is for the registration form on the UBB to post the details to the webmail system and it would create the account automatically with the same details.
So what do you say? Anyone up for the task? Doesn't seem that difficult now for all you coders out there!
P.s. In case you need a look, I'm using the EMU email system from
www.emumail.com with the WAP interface and the registration thing, so it creates accounts automatically and you dont need to create them manually.