Hi Grotbag,
I am sure I heard somewhere (probably Gardeners World!) that woody stuff like privet clippings produce different gases to the usual heap so need to be done on a seperate heap with other woody stuff :-\
Hope this helps for now although I will be watching this thread 'cos I want to learn more about composting ;D
(I am now the proud owner of a 'pallet' composting centre! It has three compartments all waiting to be used properly!)
Donna