Just to update, wasn't clear where the cable went into the CU, its a bit of a mess. However, managed to determine the cable exited from the bottom which meant could identify the route. Put another break in the cable between the kitchen and CU and found the fault was near the CU under floorboards/skirting. Turns out were two breaks in the insulation from frankly unknown causes, don't know when they happened, likely corrosion and walking on the boards brought it on. There was a break in the earth back to the CU and a crushed neutral.
Cheers!
Cheers!
