I'm about to make 3 wooden compost bins out of a quantity of left over
decking, plan is each will be about a 1 metre cube with a removable
front and wooden top. They will be in shade behind a shed.

Seems to be two opinions re ventilation, build it with the planks
close together to keep in heat or space them to allow air to circulate
(or even make the back or sides from mesh)

Most of what will be going in will be grass cuttings but other organic
waste will be added for variety (as well as ginuea pig and rabbit
straw and poo!) I also have lots of worms which will be moved from the
current bin.

I'm inclined to make it closed to keep the heat in. My power tools and
saw are at the ready, any suggestions as to the best construction
methods ?

DC