I asked Sheerluck Holmes, and all he added was:
It's spring or autumn, from the trees. Probably spring as the vegetation doesn't look lank and damp.
It's morning or evening, and facing west or east, with the sun behind the photographer. Probably morning, because the girls' smocks are spotless.
Probably 1895 - 1910 from the dress.
The small girl on the fence has been sitting there some time from her fed- up expression, so the train is probably late, or Daddy's watch is fast (again).
The loco would appear to have a front outside axlebox, so a 2-4-0.
There is a small mound of cigar ash in the right background, which is of a type specially produced for Lord Huntingtower by Carlin's of Regent Street. You may remember his rôle in the Mystery of the Dancing Badger.
Hence the scene is somewhere in the Lincolnshire Alps. The eldest of the girls is probably Marjory Bigglescastle, who you will remember as the young lady who was so scandalously traduced by Bunny Carruthers, emerging with full honour intact and resulting in his leaving for Darkest Africa, where he was eaten by missionaries.
So still not a lot to go on.