What radiator coolant to use?

[peterpsg]

Continuing on my replace-all-fluids approach to the new season - what fluid do people use for the radiator? (And how much, or what sort of water/coolant proportions !!!)

[pb3]

I was advised by the Factory to use Blue Col (2yrs ago), 50/50 mix with water. Seem to remember 17 litres total cooling capacity, so that is two containers of coolant!