Obviously a bit of a rethink was in order, which started off my headache problems. I worked out that if I made the blocks at 8" finished, and made 4 of each, with a centre medallion (possibly of a sundial) 16" square, then it would make a quilt which was 64" without borders. Perfect!
Here is my design - sorry it's a bit faint. All the circles are blocks, and then I will have to do something in the corners to make it square, but that's a decision for later.
Next headache was to reduce the instructions from a 12" block to an 8" one. I made a prototype (which was too big) and then one which was fine.
And here is my first block, measuring in at 8" finished (more or less!).
When I've taken some paracetamol and had a lie down and a cup of tea, I'll make the other three!