Try plugging your router into the hidden test socket that is revealed when you remove the bottom half of the split faceplate (2 screws) of your master socket. Only do this if you have a split faceplate. Do you have any extension sockets? Are there any wires connected to back of faceplate?
Post your full Router Stats when plugged into test socket.
Try the BT Quiet Line Test (dial 17070 Opt 2), preferably with a corded phone, in the test socket with the router disconnected. If there is any noise, report to your landline provider as a voice fault (don't mention Broadband). Often sorting out voice faults will fix the Broadband as well.
just detach the wires from the terminals on back of front plate extension will no longer work
So, had an engineer visit on Thursday and was told that they random disconnections where down to a faulty card in the cabinet, that got fixed and have had a nice steady 65\66 download 18\19d upload.
However, test the connection this morning and in 24 hours have lost 10 meg download speed.