Thanks folks.
It's a 2012 build. Just moved it on and off drive. First time nothing on either gauge. Second time working rev counter and temp gauge.
I am going to add a fuse to the trickle charger so the battery comes off on Sunday. Then I'll open up the dash (again) and have a good look.
Dodgy earths may be to blame indeed. I know the temp gauge is run off that pesky control board behind the centre of the dash - I have a spare following my heater fan shenanigans so I may try swapping that out.
I am kicking myself for telling someone that I have had the car running reliably for a year now so it is sorted - clearly it didn't like that..... Today I could happily flog it to the first bidder!
