What an absolute pig. Removing radio and dash was straightforward enough. I unscrewed control panel and flipped it over expecting removable bulb holders. Er no
Only way to access the lamps is to split the whole unit into two halves. To do this you have to remove wiring and control cables from controls. Removed whole unit from car and took it inside. The unit has some very nice aftermarket knobs on it that were pushed on with a mallet I presume. 30 mins of wrestling with tabs I finally got them off. have put some white grease on knobs in case I ever need to remove them again. Refitting wires for controls was best done with the unit outside the dash and then I carefully re-inserted it.
If the lamps were in removable holders I wouldn't even have had to unscrew it from car.
Mind it nice and bright now