Hey Roy basically what happens when you send an email is the message gets put on a mail server (virgin/ntl use Google`s mail servers now to store messages, this is why you have 10GB of storage space).
When you fire up your Email client, e.g. Windows Mail it checks with the google mail server and downloads any new messages to your computer. Sometimes these messages are deleted from the mail server when downloaded to your computer but you can choose to keep them there. Allways handy and as you have 10GB of storage space you shouldn`t run out to soon.
You can allways log in via webmail and delete any anyway.
First off from your Browser, Internet Explorer, Firefox whatever go here
http://www.virginmedia.com/customers/emailgateway.php follow the instructions put your password in and you should get into your webmail account (this is where your emails first go and are stored).
You may see all your messages there, if not you may need to adjust a setting so they are not deleted if you download them to your computer.
Click on "Mail Settings" now click on the option Forwarding and POP/IMAP. Number 2 needs to be set to "When messages are accessed with POP [keep Virgin Mails copy in the Inbox].
If it`s like that fine they are saved there allways, if not set as above and Save Changes.
Good Luck
p.s. There are a lot of people who do not even use an Email program on there computer anymore and prefer to do everything through Webmail. Also apologies if it isn`t a .ntlworld/.virginmedia.com email address