To put these block sections together successfully, all the angles need to be running the same way. That didn't occur to me when I started stitching them together.
I have since learnt a couple of things.
1. Lay the paper pieces out correctly first and mark the backs before you go anywhere near the fabric!
2. There is a weird but inexpensive tool called a tailor's awl that is just magic for unsticking erroneous basting. I suspect it will be used quite often over the next few months.
Wishing you all a relaxing and crafty Easter weekend!