(well, that should result in some entertaining Google searches)
I think I've worked out the architecture of these granny square things. See here:
(apologies for photo quality - my Paramour 'borrowed' my camera and changed all the settings, and I need to re-read the manual to find out how to change them back again. Photo below taken before my camera was messed about with. I rest my case.)
Anyway, I'm still really pleased with my progress, BUT the square I have made is much looser and holier (in the non-religious sense) than the ones in the blanket I'd like to mend:
I think I've worked out why. In my square, I do three triples before each chain stitch, and - from close inspection of the blanket, with my glasses on - it looks as if Millie's granny did four triples. She probably also had a smaller central circle - I've done a chain of six, but I suspect she used a chain of five or possibly even four. So my next experiments will be along those lines. And at some point soon, it'll be time to try more than one colour. I will, of course, keep you posted. Bet you can't wait!