@DavidMshould be calling back in on this thread. He will activate the link for you to get in touch with the mods, one of them will sort everything out with you. Don't bother ringing back in.
If the engineer turns out to be correct and they can't improve you service they will arrange the switch back to ADSL for you.
The router can be used with standard broadband if you wish.
Ah right. Many thanks for that.
I've activated the link under my profile for you. To see it, click on my user name and look for contact the mods which is on the left hand side in the about me section. It'll take us a few days to get back to you but we'll do all we can to help fix this.