You may not see much activity for a few weeks. The microherd of composter animals has to be built up first. This takes a while in a brand new bin. I would not add anything until you see activity well under way in the original foodstuff. I don't know the climate in the UK or even where you are. If it is cold at all they will slow down to a crawl in their munching. Give us a little more detail. Is the greenhouse heated, what is your average low temperature, etc?