Looking at the scale of men and loco and the loaded wagon I would say it is a Hunslet narrow guage quarry loco as used in the slate industry in Wales and the stone quarrying inustries.
Looking at the pic of the men in the shed and the Billy cans on the hooks I would say mid 1920s for this one, Normally after both wars men in industry would use army surplus material to work, snap tins, mess tins, billy cans, gas mask haversacks as "bait bags" ,these billy cans don't appear to be the military type but the enamel kind that were used on locos by the fireman and driver.
As China says the clothing is pretty much undateable and men dressed like this with the same waistcoat and billy cans and caps worked in the steel industries in the North East of England up to the late 50s.
Perhaps they are quarrying limestone for the iron and steel industries.
James