I've just replaced failed bulbs for AC and demister switch illumination, and the four bulbs for the rotary volume control. They all take T3 8mm wedge fittings - I got a pack of 10 white LED ones (20mA) from Amazon UK for £8.
To get at the volume control, you have to get the centre unit out - I didn't undo the heater cable as there was enough room to keep it in situ. I also left the 3 cables plugged into the rear of the radio unit in place, to enable checking of the new bulbs and rest of the controls, prior to reattaching the PCB to the radio unit.
Undo x4 bolts holding radio unit in metal retaining bracket, the screw on each of the 4 corners of the PCB, and the 2 little screws at the top centre of where the radio unit abuts the PCB.
Gently pull unit back from PCB. Mind the ribbon cable between radio unit and PCB. I carefully released the ribbon cable from the PCB which then gave enough room to remove the failed bulbs and install the new ones.
Check if fully seated and polarity is the right way round, by switching on side lights, if using LED replacements, and adjust as needed. Then attach radio unit back to PCB, bolt back into mounting bracket and fit centre unit back.
The white LEDs result in a red hue for the demister and AC switches and volume/audio control, rather than the more subtle orange hue of all the other controls. I don't know if this is deliberate (I guess not) but I quite like it, as the contrast aids identification at night.
I've attached some pics - apologies for the poor quality, as I wasn't planning to post