On 5/10/2018 6:59 AM, Adrian wrote:
BT line with phone and broadband.

Broadband is working OK and that has its own socket on the master socket.

I can only get the phone working if I plug directly into the socket
behind the face plate on the master socket.Â* If I plug into the socket
on the faceplate, I don't get anything at all.Â*Â* BT have suggested that
the micro filter on the faceplate has failed, but I've replaced that
with a new one, and that doesn't work either.

Any suggestions on where to start looking next ?

I've had a similar problem, more than once. The solution was, oddly
enough, replacing the router/hub. See if you can borrow one, switch it
for yours, and see if that clears the problem. If not, perhaps the whole
master socket needs replacing?
According to a local OpenReach employee, lightning strikes in the area
may have caused some damage, but not enough to stop all functioning of
the hub.
It's happened to my phone service three times now, and each time,
replacing the hub has fixed it.