Ah... Found this video online
https://www.youtube.com/watch?v=Ek_ewKeF6r4 where he shows how to take apart the switch. Mine looked pretty good but had some white ceramic dust coming out and very tarnished contacts. Took it totally apart, cleaned it with WD40 and put it all back together. Quick test and it's working like new again! Saved £150 on a dealer new part!
Now to get it all back together.
One thing I did notice was the lights/sidelights indicating bulb that's in the assembly had a broken bulb holder. Anyone have any idea where to get a replacement and some replacement bulbs? No part numbers on the actual items that I can see.
James