As Jim and Dickie know, when I tried to start the car with a flat battery, the rev counter needle flipped right around the other side and had stayed there since. I was advised a small wire through the trip counter button hole can bring it back round but I abandoned that idea as I realised I was scratching the dial face in my attempts. I managed to move the needle up to about 4/5 O'clock but it soon dropped back down
Funny thing happened though, on restarting the car, it's now working

Which is nice

as I didn't fancy the alternative fix.
Cheers Jim & Dickie.