Thank you so much. I've had Hercules and Horace since I was five so I don't want to take any chances! I'll buy a thermometer as well to put in the shed.
I have two Greek tortoises which are very old. We have had them for 36 years but the vet says they are at least double that. They usually go into hibernation around now in boxes into the shed but have dug themselves very deep in the garden. They have done this before and surfaced in March but...