Hi everyone, and thank you for taking part

Toni, the Phoebe Tatham mentioned in regard to a divorce is not our Phoebe, I'm afraid (I had found that one a while back) - that one would have been a Tatham by marriage, where ours was born a Tatham, and only ever married to Mr Brown. It was, I believe, Phoebe travelling as "Mrs Brown" who accompanied the children back to England - will check my notes again to be doubly sure.
Thank you for that link - thanks also to Lizdb for her one - I hadn't found either of them before!
Oo-er ... second edit

... the half-uncle Christopher from whom Duncan John inherited money ... was his half-uncle Christopher Tatham (son of surgeon Christopher and Elizabeth Gordon Tatham) ... so no connection to the Dunbar estate.
The Duncan Tatham who comes up on the electoral rolls is the right fellow, ... but the entry is a glitch; - I found him via the local Library's Ancestry link. The date for his voter registration was actually 1856, from memory, so no idea how it found its way in amongst the 1901-1936 rolls

All your help sincerely appreciated,
Deb