Okay, I decided to work at home on Friday (not an easy task given the bandwidth) just in case BTW needed me to be at the PC. The phone rang at 10:45 (I had been told to expect a call between 9 - 11 so very good. Sky advised they were still awaiting a response from BT and would be back in touch but there was no time expectation.

I decided to go back to the office at noon, just before I left I ran the speedtest again, and woot straight up to 2.5meg. I have been checking it every half an hour so was very suprised and very pleased. Better still the line's latency halved. I have no follow-up call from Sky or BT, but not bothered.

Thanks again for the help given to me here, hopefully other people with the same problem can follow this blueprint for getting the issue resolved.