Hi nb31
Thanks for posting and welcome to the community.
Really sorry about the no dial tone and I do want to help you sort this, hopefully remotely as will be quicker.
I've ran a few checks on the system and can see no outages which is a good start. Are you plugged into the master socket? It will have a larger socket and contain a logo of Virgin Media, NTL, Telewest or Nynex. Any extension sockets will be smaller and have no logo.
Let me know if it's an extension or the Master socket and we'll proceed further.
Kind regards,