Hi,
I've been looking into my own Leaf family tree, and came across your post - maybe there's information to share!
my ggg grandfather was William Leaf (b.1807), brother to Henry (b.1814). William married Jane Meyrick from Bishops Castle, Shropshire in 1830, and yes, two of their children were born in London, though I've yet to understand why. The family were back in Howden after that, as their other children were born there. William was a tailor/master tailor, as was Edward his father, and some of his children/grandchildren.
I've been trying to map out the other Leafs in Howden, and trying to see how they fit together. When I was looking at Henry and his branch of the family, I thought he married Elizabeth nee Richardson, from Bubwith, b.1814, and that it was one of their sons, John Edward, also a vet, who married Elizabeth nee Barr, b.1845 from Pickering.
Oh, and in Pigot's Directory for Howden in 1834 Jane and Mary Leaf are registered as Milliners and Dress Makers in Church Yard, Howden. Mary could be one of the daughters of Edward and Mary, b.1811 (never married as far as I can tell, lived with Henry and family in some of the censuses), or Mary her mother. Jane could be the wife of William (the one nee Meyrick mentioned above), but I'm unsure. I can't find any references to what happened to John, b.1809, so don't know if and who he married, or when he died.
There seem to be links to Leafs in Sculcoates, and also York, but I haven't been able to figure them out yet. I've only traced back to Edward and Mary, parents of both William and Henry. Does any of all of the above help? Have you got any further with your own research?
Phew that's lots of bits of information and many unanswered thoughts!
all the best,
Helen