In reply to UKC/UKH Gear:
"At £30, plus the running cost, it's not wildly expensive."
I see it's essentially the same insecticide as a mosquito coil.
£30 plus proprietary refills is a lot more expensive than a mosquito coil holder at about 6 quid. The added bonus of the ones that sandwich the coil between glass fibre nets is that you can burn it at both ends. Or break it in half and burn it at 4 ends, or more if times are desperate. The coils are cheap, leave no waste apart from a little ash, and come with no plastic packaging. Also it's immediately obvious when they've run out - is that the case with the Thermocell refill thingy?