CANCEL PANIC!!!
Turns out I was correct, the housing at the top left contains just 4 simple keyboard switches which are daisy chained and linked to the PCB with a common earth.
After MUCH deliberation (and a couple of vodka’s) i decided to open up the handle and have a look-see.
Found that 2 of the common earth wires had come off hence causing 3 switches to be u/s.
Housing popped out and wires soldered - fully operational and VERY HAPPY!!!
Learned a lot this evening!!!
FlyingSpanner