Thanks Roger. Without a block drain, it seems that the system would need to be refilled with clean deionised water, run to get it mixed and then flushed out, and repeat several times to get rid of all the old stuff before adding 5 litres of antifreeze concentrate and topping up with water.
I have concluded that if I just refill with 50/50 on top of what is left in there, I won’t be alone in the world by adopting that approach. As I bought a 5 litre can of antifreeze, I guess once the new rad is fitted and engine run, I could drain down just once and refill with 50/50 and so use up what I have purchased.
