We've got anything up to fifteen people coming at the moment (if Deano's list at the start is accurate), so we will probably need a couple of cookers anyway. Likewise with that many people, we'll also probably need a couple of pints of milk to make enough mugs of tea/coffee, and people are likely to need to bring their own cups (or use someone else's on a time-share basis!).
I'm happy to bring a cooker, largish pan and lid, a pint of milk, my small camping containers of coffee, sugar, and tea bags, a teaspoon for stirring, and possibly another pint (or so) of water in addition to a water bottle of water, to cover for people who aren't carrying a pannier, and don't have much room for water bottles on their frames. With addition of some cake, that should provide a reasonable halfway break, assuming we can find somewhere not too windy to eat and drink.
