Thank you, all, for your replies and suggestions. I suspect that aside from uninterrupted supplies of insulin, test strips and (for the last two years) Libre sensors, my NHS care has been a bit superficial. I'm certain it was never, ever suggested to me that my HbA1c could or should be taken more often than annually.
I suppose that being active, diet-conscious and happily finger-pricking very regularly, I may have seemed to be largely self-sufficient in the eyes of the diabetes nurse I see every 12 months, especially compared with the many patients whose results aren't so good. Actually, when I look back at earlier results over ten years, my history is mixed at best, but that makes me keener than ever to keep things as near to perfect as I can make them.
I had heard of CGM-estimated HbA1c readings not aligning closely with the real thing when it is taken, but after my real reading of 5.4% last year, I was content to see my Libre steadily showing around 5.5%. Unfortunately that seems to have been optimistic this year. I'm not downhearted - just determined to do better.
Many thanks for Thriva suggestion, and the Amazon option...if I can't simply arrange three-monthly tests with my local health centre (Southampton seems extraordinarily over-stretched healthwise) I will do it myself.
Thanks again, to you all. Great forum.