Just to conclude (happily) this long saga:

The BT man (well, contractor working for BT), came on Monday and did the installation and the speed has gone from my previous 2 MB to an awesome 61 MB. I understand that the line speed may settle down to something different as the balance between speed and quality is automatically assessed by the BT systems. But at 60 MB, I'm really pleased with the new service. Everything is, well, fast!

Good luck to everyone else and I hope that you don't have to wait too long.