Had exactly the same last Friday night. Had just got onto the A75 when the temp gauge dropped to zero. Stopped immediately and switched off. Checked the expansion tank etc, and all seemed well. Started Roxy and the gauge registered as normal, accelerated and the needle dropped to zero.
As I was nearly 3 hours from home I pressed on. (How many levels of paranoia are there?)
Got home and spent Saturday morning checking. All was well behind the instrument cluster, so took off the engine cover and checked the temperature gauge sender. (The blue one underneath the pipe.) It had been held on with a zip tie that had broken, allowing the connector plug to work loose and make intermittent contact. Pushed it back on and zip tied it in place. All functions back and having done 300 miles since, all seems well.
Hope your fix is as easy.
Winko
Thanks - think I have bought the wrong one then - or are they both the same?