Hi Nige, I am no expert on the various types of coolant, but being a Lancastrian I am quite expert in getting value for money, so I would be inclined to use the Halford's voucher on getting something useful as the best quality car shampoo or engine oil. I would also check with Halfords --- they do have some useful mechanics --- if you can mix the various types of coolant, as they all do the same job. Regards, Peter.