I've finally got around to having a look at the problem.
The clock unit is quite easy to get at.
Open the ash tray and remove the inner ash box.
Undo the two self tapping screws behind it and pull the whole unit (door open panel, hazard light and clock) toward you. It's held in by a couple of pop fastner type pins (1997 model, I assume the rest are the same).
The unit comes out as a block with three wiring conectors in the back.
Unplug the conectors and Undo the two allen bolts at the corners, the unit is then free. It's held together by 4 or 5 Torx screws, if you find your problem isn't the wiring and need to be into the unit.
I don't think the radio has to come out, but mine was out any way as I was fitting a new one.
Hope this helps.