Thank you, Barty, that was an impressively fast response.
I had seen that memory module on the Crucial site, but my problem was that I started to look at other combinations, and that's when I came unstuck, and by the time Kingston, Corsair and Ebay were finished with me I was a quivering bundle of uncertainty.
You have restored my equilibrium, for which many thanks, and I will of course follow you suggestion.