That was my original plan at bottom of garden, half burying some ibc's and building around the top, can't sink totally it turns out my house is built on what used to be a car park and they left it under the garden 2 feet down.
Current plan after reading this months window cleaning magazine was 6 water butts down the side of my mates garage (which has a radiator in which is connected to his house). My guess is the water in the middle ones (using overflow from one to another) would get warm and stagnant at the bottom although moot point anyway as I got one up there at the moment and it isn't collecting enough so back to plan A.
Current plan after reading this months window cleaning magazine was 6 water butts down the side of my mates garage (which has a radiator in which is connected to his house). My guess is the water in the middle ones (using overflow from one to another) would get warm and stagnant at the bottom although moot point anyway as I got one up there at the moment and it isn't collecting enough so back to plan A.