Hello, I hope I can offer you some assistance.
do all the side lights work as they should? Is it just the illumination for the cluster and number plate that isn't working? Does the heater control illumination work? Do you have the chassis number of the car? So I can obtain the correct wiring details.
Let me know and I'll reply as soon as I'm able to.
heater control illumination is not working.
chassis no WFODXXGAJD8A40490
look forward to hearing from you
to start with check the heater panel and cluster illumination. As you say the fuses are OK we'll assume there is 12 volts at these. Check at the headlamp connector pin 13 (orange/blue wire) for 12 volts with the lights turned on, if there isn't 12 volts here but there is 12 volts at pins 8 and 11 of the lamp switch then the switch is faulty. It's unlikely to be an earth fault given that the cluster and panel illumination don't work as these use different earth points. If you have the ignition on and use a fused jumper wire between pins 11 and 13 of the light switch the number plate lights should come on, if they do this would confirm a failed light switch.
Start with checking these points, let me know if I can assist further and I'll reply as soon as I'm able to.