Hi Bluebell,
In actual fact with composting size does matter!
The bigger the bin the more you put in, the hotter it gets.
Obviously you also need to be reasonably careful about keeping the carbon/nitrogen ratio right. I would stress reasonably careful. Home composting is not an exact science and you will find from time to time that you need to tweak the contents to get/keep the process going.
For instance if the contents get too dry or too wet or very smelly.
When I say turn I don’t literally mean turfing out the contents and then refilling. I simply dig over to a Forks depth and this only takes a few minutes. Turning in this way on a regular basis produces usable compost in 5/6 months and if you get the timing right you will always have compost when you need it.
Don’t get me wrong, I’m not decrying the Hot Compost Box system but I can’t really see the need for creating compost in 18 days. After all you will, using no-dig, for the most part, only need to apply your garden compost once a year. Of course you will use it at other times for other reasons, earthing up, etc., but for the most part you will only be using it for top dressing your beds in Autumn/Winter.
Don.