yitzak writes
Thinking of getting one - local council is offering them quite cheap.
The sort that the compost just drops out of the bottom flap.

I would have to stand it on concrete floor and my garden is v.small
(4.5m x 4.5m).

I cannot see how they can work well because how does the air get to it??

There will be plenty of air in amongst the stuff you put in. It's only
when it's very densely packed that all the air is squeezed out of it.
--
Kay