Went to Halfrauds to get OAT concentrate antifreeze (the pink girly stuff)
"we don't stock it, can get some for tuesday "
so, following TB's example , I walked
(even though there's 2 cars outside) to the local independent parts factors ,got 5 ltrs for less than 12 quid
part drained Mrs Builders coolant and added the concentrate to ensure it was strong enough for the impending predicted zero kelvin ice-age