Hi guys thanks for the replies
OK I've sorted it, so much is similar to the stereo removal but nothing quite as dramatic.
So firstly remove the cigarette tray, then the rubber mat underneath the tray.
Unscrew the hex screws behind where the cigarette tray was, this removes the outer cover of the air con facia.
The big central dial is what I needed to change, so at 6oclock looking at the console dial there's a small plastic catch, lift this and the outer dial surrounding the knob lifts off with a wiggle.
You can then pull the center dial off and replace or take off the silver ring, which is held with catches if you don't like the effect.
However on replacing be carefully there's a small metal catch spring below the dial which must be inserted on the outer plastic dial housing, before relocation. As I didn't see it to start with and the temp gauge wouldn't work.
Once done it's an easy refit as above.
Took 10 mins with learning about the metal spring clip and all sorted.
I hope it helps others, actually having no silver ring and just black looks nice also.