U.K. Mess Kit
Set of square UK mess tins with Knife, Fork, Spoon (KFS)
Set of square Dutch mess tins with KFS
Do not buy WWII tin plated ones from Wephaus, they are not safe to eat from. The later aluminium WWII versions are ok, but the modern ones are cheaper and safer. A search for Dutch mess tins will also yield safe to eat from selections and they are virtually identical to the UK tins, or you can just order current mess tins from the UK. Mess tins available CONUS: http://onlinemilitaria.com/shopexd.asp?id=1050&bc=no. If you are using British Army Rations you'll need these in addition to a hexi stove or small pocket gas stove to heat the retort pouches contained in the ORP rations.
Knife, Fork, Spoon (KFS) there are several military sets that clip together to make the parts easy to find. You may also prefer to use metal canteen cups in place of the mess tins to heat your meals.