Re: There's also a value to keeping your email address
Ah, but your ntlworld.com address is reliant on someone else maintaining that domain and service - so when Virgin (or whoever they get sold to in the future) decide to drop it, you'll still need to get a new address.
By owning your own domain, you are in full control - you can switch email service whenever you want (or host your own if you're up for it), and no-one else can muck you around.
The sooner you switch, the less pain you'll suffer in the future. There really is no reason to use the email address that comes with your ISP for anything, other than receiving the ISP's junk...