I have grown tomatoes in my 6' x 8' greenhouse since I bought it three years ago. It has a concrete floor, as a summerhouse previously occupied the location. I plant my tomatoes in growbags standing in large rigid plastic trays, available from B & Q or similar, a few inches longer and wider than the growbags. To maintain a steady supply of water, I used a knife to cut small slits along the sides of the growbags at about ground level and I keep water in the tray. When I feed my tomatoes, I pour the water and fertiliser in through the top of the growbags. This system works for me, as only a handful of tomatoes have split each year and, as has already been said, they can be eaten, as long as they are not mouldy.