You'll be able to send through ntlworld's SMTP server only if you're connecting to the Internet with Virgin Media (and hence picking up a suitable IP address). As you won't be connecting to VM while you're in China, you won't be able to send mail through Outlook.
Your best bet for now is to use Web mail to send messages while you're away from home:
When your mail account is migrated to the Google platform (probably next year), you'll be able to use authenticated SMTP, which means that you will be able to send mail via Outlook regardless of your Internet connection method.
-- I have previously worked for one of Virgin Media's partners. My personal site: http://espirian.co.uk/
Thanks for replying (when I enquired previously, the support staff could not explain why I couldn't send emails on my travels, via WiFi or dongle, in Scotland and Spain.)
However, the reason for using Outlook is to have a unified email system, with the capability of synchronising the messages on laptop and desktop, and maintaining a complete record. Messages are soon deleted from Web-mail, by the 'system' rather than user. The necessity to use web-mail to send messages when away from home is messy - a copy of the message sent has to be to myself, so sent messages end up in the Inbox. Please expedite sorting out this bug so that emails can be sent from Outlook when away from home.