Well today's trials have gone well. Using warm water left over from the 1st trial, pasteurisation temperature was reached after only half an hour with 6 bottles of conditioned cider instead of the one on the 2nd run.
The first was sampled on cooling, and apart from being a little cloudy tasted good with no evidence of heat treatment.
This process will kill off yeast organisms and allow for stabilisation of any cider but especially ciders with more added sugar at bottling ie. medium sweet/sweet (thus removing the risk of continued in-bottle fermentation with the accompanying risk of burst bottles)
A cage to hold the bottles would make the process more efficient though.
Author and food scientist - noted specialist in cider - in his excellent 'Craft Cider Making' (above) advises wearing goggles and strong gloves when handling hot bottles of conditioned cider.
Bottles cooling outside: