Just in case this information can help anyone, I'll share how I set up my small cave.
I had an electrician friend set up the controller on the small fridge with the heating phase of the controller connected to the fridge light.
Its a surprise how much heat is generated by a small globe inside a closed fridge.
So now the refrigeration starts up to get down to temp but with the heating facility, the light comes on to raise the temp.
This allows me to use the cave for various early stages where temperatures of around 20-22C (68-72F) are called for.
I also use the fridge to mature cultures at around 30-32C (90F).