how to change domain name

[#1]

I have a domain name ending in force9.co.uk. I want to change this to a new domain name ending in .uk.com. I haven't registered the new name yet and , before I do, I want to be sure that it will be possible to change the existing domain name. I am on Broadband Plus.
Thanks...

[#2]

You can't change domains (that is inextricably linked to your user name) but you can ad a domain on to your account which means that emails sent to either something@username.force9.co.uk or something@yourdomain.uk.com both end up in the same mailbox. You will also be able to set up a website for the domain.
You have compared the cost of .uk.com to .co.uk I hope!