Hi Icaras,

Opinion so far seems to favour a rectified loop. I'll have a look at the socket if I can to see if there's anything obvious.

You do need to confirm where the line enters and the first socket/junction box. If there is not a master then you will need to get the situation "normalised". BT will normally do that free for their customers, however I do not know what TT will do or charge. Locating a master or getting one installed has to be the first step.

If you can find that and then remove all other wiring you will either remove the fault - in which case it is on your side OR if the fault remains it is the suppliers responsibility.

Firstly, apologies for the delay in responding, been away at a funeral.

So, in line with your first reply (Tuesday), I've requested the line transfer to be enacted, and they're putting in an exchange call forward. I can then deal with the fault once we've completed the purchase. On to your latest response:-

In reply to a post by MHC:

You do need to confirm where the line enters and the first socket/junction box. If there is not a master then you will need to get the situation "normalised". BT will normally do that free for their customers, however I do not know what TT will do or charge. Locating a master or getting one installed has to be the first step.

If you can find that and then remove all other wiring you will either remove the fault - in which case it is on your side OR if the fault remains it is the suppliers responsibility.

Agreed that I need to establish where the line comes in, and it looks as though I'll be pulling up some flooring - deep joy! Once I've established whether the existing extension box is in fact the master I can then disconnect any other wiring, if it exists, and then confirm whether a new master socket is required. My strong suspicion is that it will be, but we shall see.

This is all good info and very helpful. Thanks a lot.

Update:-

Just to bring things to a conclusion, lifting a few flooring panels I was able to confirm that there was no extension wiring, and the ISP confirmed that it was a loop fault. I put a call divert in place and the building re-furb work recently got to the point where sorting the problem could usefully be done without disrupting the builder, heating technicians and electrician. The fault has been cleared and a brand new NTE5 installed. All good!!

Thanks for everyone's help and comments - all very much appreciated!