...the Mains supply is screwed directly into the back of the blanking plate (type thing) in three rows (is this called a junction?). These rows are actually moulded into the blanking plate (type thing), to house the metal fixtures that comprise the junction. Wires coming out of the junction then form into two cables - one going to the boiler, and the other going to a plug that plugs into a socket on the wall adjacent to the blanking plate (type thing). When the plug is in, the power supply to the boiler is connected.
The blanking plate (type thing) looked exactly like the ordinary white plastic socket next to it - minus the three holes for the plug, before it was smashed. There was no hole in the middle so the cables must have snuck in at the sides/bottom. There's a kind of metal back and frame that the blanking plate (type thing), screws into. There's also a sperate clear plastic junction for black (and maybe red) wires that hangs around in that space. The junction part of the blanking plate (type thing) is still intact - and I was hoping to get the exact same fixture to replace it, without having to remove it, as, being no expert, I could then retain an idea as to what wire goes where, re-wire the junction part one wire at a time, then screw the new blanking plate (type thing) back into the metal frame in the wall.
thanks all for the input...