Time for an update.
After much consideration we've decided to change our phone and broadband to Sky. In addition, I managed to negotiate a half price Sky+ box with free installation
We should have phone by next Wednesday, having transferred our VM number to the BT line.
Broadband will start from 22 July.
Sky+ is being installed on 4 July.
I'm glad I came here for help, you guys have given very useful advice so thank you
Finally, with regards to the original thread topic, the official BT line installation charge is £124.99 and all the engineer did was put a master socket on the wall and attach some wires in the green box down the street. He said I may not be charged but will have to wait and see.
Even if we do pay the whole installation charge, we will have made up for it within 3 months from the amount we should be saving on our monthly bill.
Thanks again.