First of all, thanks to everyone who came to my aid, much appreciated.
The temperature has dropped by 10° and the fridge has been in shade overnight. It is now working fine, so those of you who thought it was the heat, Well done. It never even crossed my mind cos it's never happened in 11 years, still you live and learn.
I never knew about setting the stat too high either, so another lesson learned.
What can I say Colin?