Interesting discovery - depressing the brake pedal, brake switches both went from inactive to active; depressing clutch pedal, nothing changed, it read active pressed or relaxed. Contemplate.
So the ECU cannot see the clutch switch.
I'd check it by replacing clutch switch with a suitable bit of wire, to see if wiring OK (on live data only, not for driving), and if it makes no difference, then get a meter out and start checking the wiring.
I removed the clutch switch lead, and after a struggle inserted 2 wires in holes 3 & 4 of the socket. With the 2 wires unconnected, connected diagnoser, and discovered clutch switch was still 'active'. I removed the wires from socket, and diagnoser still said 'active'.
Looks to me that the 2 wires from the clutch switch are shorted together somewhere. I can see some white (masking?) tape around the pair of wires higher up, but can get neither a good photo or conclusive view.
Please advise.
Is the instrument panel easily removed, as on the Omegas?