First I would send an email to
neil.berkett@virginmedia.co.uk the CEO of VM so that someone could take ownership of your issue and you would only have one person to deal with until it was resolved. Saves all the runaround you are getting.
Be polite, request help with the issue and copy and paste your OP into the email.
Then
I would get onto a solicitor to persue a claim against the building site construction company for loss of services caused by them.