In the interim .. (while I'm having a lunchtime sandwich)
The master box is part of the Service wiring (and up to it)
So the provider is responsible .. 'officially'
However .. No-one has a record of what is fitted at what property ..
Many people have fitted their own bought master (a BT or other copy master)
There are two wires to screw-connect to A & B. 10 minute job to swap boxes.
Then the extensions (if any) are connected to the adapter faceplate. When you take the adapter faceplate off, there is a 'system' socket behind ... the incoming connection. This enables one to disconnect the house system from the main connection .. for testing. Quite useful really.
Do you have any other lines in the house that have to be connected to the main inlet socket?
If your router plugs into the main inlet socket ... I should get one of these ... and plug the router directly into the ADSL connection. If it plugs in on an extension somewhere, just connect as normal and leave the ADSL outlet on the master un-connected of the front. ; )
http://www.ebay.co.uk...L&hash=item3a6ce47e8f