I also tried to direct through GMail, but my messages were just arriving FROM my actual GMaill address (IE the header had been overwritten, even though the message originated from my own domain) and so it looks like I'm back to smtp.ntlworld.com for now.
I found a post on the forum saying about adding another email address to your Account, using @virginmedia.com as the domain, which I went to do - but unfortunately:
"We are currently in the process of upgrading our email system. You will not be able to add or delete any mailbox during this time. As soon as the upgrade is completed you will be able to add and delete your mailboxes again."
So I guess it's a case of waiting...anyone got any clues as to how long?