billycat,
u're right asda do have but it's in a plastic container not the cardboard 1 ltr that i've seen malik use. i can get the cardboard version in bolton and i suppose holding out for that. i was not convinced by the label that the asda UHT was the same stuff (gave the impression of more like double cream).
the fresh single cream from asda was what i used and worked spot on.
the interest in the UHT is a belief that it would freeze better as long term i see me making this sauce in larger qty and freezing leftover.