My thanks to all of you who responded with suggestions, all much appreciated. When the thread was given a new lease of life I took a closer look at Michael Fannymore's suggestions, and went for a Post Office travel money card, which fits the bill perfectly.
It's basically a pre-paid debit card, like you could buy anywhere a few years ago; to load it with the £50 minimum costs £53, it works on AW, and is the perfect solution.
Thanks again to you all
