And normal service was resumed!
After much fiddling and exploring I found myself in an area called ‘Delivery Settings’. Towards the bottom of this page I discovered a button which said (para-phrased) ‘check to block e-mail posts from sites you follow’. Now, why exactly you would want to NOT receive e-mail from someone who you have chosen to follow and receive mail from, I do not know – obviously someone somewhere thought it might be a good idea!
Anyway the upshot is that somehow this button had been inexplicably ‘checked’ (whether this is due to WP, my server or m mobile I’ll probably never know), and with just one click my mail box is filling up nicely. Now I can get down to a bit of reading!