OK guys, thanks for the feedback. Looks like the steering wheel doesn't need to come off. Ho hum...you can't win 'em all.
I tried to access the displays about a year ago with my silver XM and gave in because I couldn't get the dash past the top column shroud. In addition I couldn't get access to the two screws behind the top shroud. When I went to do it recently I assumed I'd failed last time and took the step of removing the wheel. Looks like I should have persevered without taking it off. Now if I'd had the benefit of this forum at the time...........
Anyway, look on the bright side. If you need to dismantle the radio controls or the airbag then you have some pictures to show how.
If I understand correctly the screw behind the air vents only needs to come off when you're removing the instrument cluster but not for the displays or the warning light panel. The spring clip didn't give me any trouble so I didn't mention it.
Whilst the whole job appears involved, it was actually quite easy. Stopping every two minutes to take photographs and checking them on the PC before preceding is what took the time. Photos aside, I reckon I could have the display out of the car in 15 minutes or less (not including the cup of tea at the beginning whilst waiting On the airbag discharging). Like all jobs it takes a while the first time but after that the time is greatly reduced.
Look slike Citroen changed the design of the dash from screws to clips sometime in the cars history. Does that mean that the actual displays are not interchangeable? Did the change take place between S1 and S2? If so then they weren't interchangeable anyway.
Can we have a photograph of the style with the different mountings for comparison?
Cheers
noz