My definition of 'a communications company' is 'a company that it's impossible to communicate with'! (BT is probably the worst but most others aren't much better).
Like many major companies, Virgin Media doesn't give out email addresses to the general public. (It's a security issue). However, while many other companies provide a web form as a substitute for an email address, Virgin Media doesn't.
If your enquiry relates solely to your mobile phone account, try a text to 07533 016 422 (which might need to become +44 7533 016 422 from Thailand).
If you're concerned about an account for landline, broadband or TV services, try a text to 07533 051 809 (or possibly +44 7533 051 809 from Thailand).