Had I got them the wrong way round?
Well, further clues seemed to support this possibility: when he died his will was probated by Frederick Helmore Kempton, who really was a son of John.
So I've just spent a 'few' minutes swapping Thomas, son of George, for Thomas, son of John! Complicated but, whilst I'm cross that I got them wrong, I'm pleased that they're now in the right place.
Probably......
More soon.