Hi Ad, that looks a fine job you have done there. The HEATER CONT LED should only light up when you are at the HTR CONT position of the Function switch.
The HTR CONT LED is isolated by Relay 2 which is de-energised for the LEAK and TEST positions. Check Relay 2 is energised at HTR CONT but not at the other 3 positions of the Function switch.I have attached the circuit of this section again, it is different to the original to stop valves with heater cathode shorts from shorting the -45v supply. This supply also does the leak tests so the main High Voltage tests are not switched on at the LEAK positions. Just don't try it with the Function switch set to TEST