Hi Paul
You never ever listen to me but here goes.The heater you've located should be called something like a parascens and retail in homebase for £27.
It cycles and soon switches off, any lower than 5 and it wouldn't really come on at all.It has one kilo and two kilo settings.This is the tool for the job, it will not run for very long at all, and the frost settings you are thinking of are not practical.If you invented such a thing it would not work.
This particular heater is better made and more robust than other products in this catergory and is also suitable for the back of the van
Hop
Just to prove you wrong I will go to Homebase and buy one
I was only trying to save electricity because I was concerned that it would be below 5 in there for most of the Winter.
£27 sounds like an OK price too. I did see cheaper when I was looking but I felt they might not be up to the job.
Anyway, my local Homebase is barely a 5 minute drive.
It won't be used for the back of the van though because I can't park near enough to my home. It's a flat set back from the road and I can't even be sure that I would be able to park in the same street sometimes.
My static unit is about four miles from home in a little place that I rent. It's not always convenient when I'm working in the opposite direction from home but it's a very useful place to have discovered. I've been working that area for nearly 20 years and only got to find it by a stroke of luck a few months ago. Anyway, it looks like I will be doing a bit of insulating at some point - possibly with reflective foil on the surface.
My current RO is just about coping but it's stuffed really. Too much waste. Too little production. It's just about keeping ahead of me.