If you need the master socket because your broadband is FTTC that requires you to plug the router into the socket , (possibly via a filter , possibility an interstitial master socket ) , and the lack of socket in effect means you have no broadband, simply report your broadband faulty , you may need to be creative when reporting the ‘fault’ , when the engineer is sent out , explain the issue, and they replace the missing socket , assuming that the wiring is still in place it should be an easy enough ‘repair’ .
Its likely to be a chargeable visit , but you seem prepared to accept that some cost is unavoidable.
