went to use my phone yesterday and found i had no dialing tone,so removed the front plate off the openreach 5c mk 4 socket and plugged in the phone to the test socket and it works fine, so i suspected the extension line so i removed the extension cables from the openreach socket and re fitted the front and i still did not have a dialing tone so i unplugged the cable to the modem and still no dialing tone , so proving the extesion cable is not at fault, do the fronts of the openreach boxes fail, i have plugged an old filter in and broadband and phone work fine before i contact BT I was wondering if this is a known fault with these boxes.
The 5c can be a bit iffy with not making good contact. Make sure the front plate is firmly clipped in place. I would unplug the hub completely whilst attempting to get the faceplate to make a good connection and restore dial tone or DLM might take action with the multiple disconnects.
can the connection just drop after 12months of not being touched
Most likely a high resistance connection caused by oxidisation of the connecting surfaces. You could try a spray contact cleaner like Servisol Super 10, its usually very effective. Its also good for removing sticky residues.