Lots of info here... Here's all I know:
The master socket was moved because it was in the hall - totally inconvenient place.
In the hall there was a plain-fronted socket that looked like all the others, with a blank plate next to it. This was the master socket.
The ex-BT guy moved it to the study and replaced the plain plate with an Openreach branded split-fronted one.
Now in the hall there is a plain looking phone socket, which in theory is now an extension of the master in the study, and the blank plate next to it is still there.
I will tell the OR engineer the master was moved by BT. I would assume he would then know if this would result in a speed drop.
I'm straining now, but I think there was also another reason for moving the master (this was over four years ago so I'm trying to remember), something to do with the fact that the master should have been in the study all along.
Right now, if the front plate of the new master is removed, the socket that was the old master doesn't work (as would be expected) - I guess this means the new master cannot be an extension of the old one, as I was fearing.
Edited by deleted (Sun 09-Feb-14 18:01:54)