This rather small and tatty picture – another eBay purchase – shows a group of men sitting on a quayside, which may be Salonika. The mixture of service dress (as worn in the UK and on the Western Front) with a sun helmet would certainly be appropriate for men of the BSF after about mid-1916. The extremes of the Macedonian climate make all sorts of combinations of dress possible which, for me, is one of the fascinations of the campaign.
The picture is labelled ‘Somerset Miners’ which, if it is correct, suggests these men were members of one of the Wessex (TF) Royal Engineer Field Companies attached to the 27th Division. Formed as the 1st Somersetshire Engineer Volunteer Corps, they later became the 1st Devonshire and Somersetshire RE (V) and, in 1908 with the formation of the Territorial Force, those in Somerset became the divisional engineers for the Wessex Division. You can read more about them on this Wikipedia page: