Just removed the first face plate on one of the extensions, and it appears to be another master socket
. Has capacitor, resistor and surge protector. As it is a fancy brass faceplate, will probably simply snip the components off, but I'll look at the others first. It also has wires in 2,3,4,5 - so need to remove the earth and bell wire.
2nd extension I open appears to be LJU2/2A - with capacitor and and resistor. Again 2,3,4,5 connected,