All very interesting, but perhaps still leaving me in a bit of a haze. I'm not keen on going with my instincts - I prefer evidence if I can find it.
The wedding was in a Catholic church - copy MC attached in case there's more to be gleaned from it.
No I haven't found John and Lucy together or any evidence that they ever married. As far as I know they had no other children together.
I had also wondered about the name Dorette (which is the first name on the BC, which as you observe did not include Flora, the name by which she appeared to be know to the family - her death is recorded as Flora M.D.S. McDonald - I have the family's memorial card). On her Wedding Report she appears as "Miss Flora McDonald, daughter of Mr John and Mrs McDonald, Scarborough". Neither of the bride's parents are listed as guests although presents include a gift from "bride's father". I also have a photograph of her inscribed "Flora Marie Dorette Sophie Macdonald aged 18yrs about 1896"
My Ancestry DNA results (which I realise are only a rough guide) give a breakdown of 54% North East Scotland and 36% Ireland, which is hard - though not impossible - to tie in with any recent German connection. The DNA results are doubly perplexing as I've traced my maternal grandfather's line (in theory accounting for 24% of my DNA) reasonably convincingly back to the mid-1700s confined to Suffolk and Essex.
Sorry if I'm rambling a bit but this thread seems to have brought me quite a long way and , as ever, I'd like to get a bit further.
Thank you both.