Thank you for the answer!
Looking again at my tree I see I HAD noted the gaps when I failed to find a probate entry record for my great grandfather who died August 1900, but then FORGOT all about them when searching my Cornish Civil Engineer (great-uncle's grandfather) who died August 1903!
I must be just the right age (actually 67) to have several ancestors who died in the period where there are gaps in the registers!
All is clear now, and maybe this new topic will now be redundant? But you never know. Someone may have a different query about these very useful registers!