Allan -
Thanks so so much for your help!

I feel like I have been thrown a life preserver!
This is what I know & what I have gleaned. Frederick Cubitt was my gggrandfather and I have two items with the name Mary Churchill on them - a sillhouette (oh, yes very helpful to determine what she looked like

) and a teeny Bible, inscribed, I think, with the date 1807 (it's someplace safe right now). I have a book on Bowmanville (where they settled in Canada) which says that the Cubitts' first residence was named Erpingham, after their ancestral home (or something to that effect) and lists the father and names three sons as having emigrated - no mention of a wife (of any name) or another son. Three of the four boys I mentioned are all listed in the Erpingham St Mary register 1813-1880 Baptism project with Woolmer (various spellings) and Mary as parents; the birthdate of the eldest,Richard Woolmer, I made a stab at from my Bowmanville book. I hadn't seen the other entries with Hatai/Hattie and I don't find them on the page nor anything with the name Nancy, I am afraid. So maybe I am looking at the wrong church records? It's just that Woolmer is a rather unusual name, so I thought I had hit pay dirt.
And yes, sorry, I knew that it was Oulton where Frederick & Rebecca were married. Her family (the Woods) were from there. I 'misspoke' in my typing!
It didn't occur to me that Mary might not have been from Erpingham because there was another Churchill (a Joseph Dixie) also listed in the forementioned St Mary birth register - maybe a brother, though, and not her father? I had assumed the family were from there (oops).
The name Frostenden was completely new to me and I am looking forward to scrabbling around in the parish register you so kindly linked! Just glancing at it, I already have seen names that I recognise. I also will have to check how far apart Oulton and Frostenden are.
Again, many many thanks!

Daphne