After asking on various ships-sites, I think you probably are very close to an identification.
As I said previously, this is NOT a former Belgian or French packet-boot Ostend/Calais/Boulogne Dover. The superstructure is absolutely not the same.
With the large winch on an open aft deck, could certainly be a paddle-mine sweeper. A former commercial paddler under requisition, why not ! This could be thus a White Ensign.
About the naval personnel aboard whilst being scrapped, on the enlarge picture/negative one can see that they are wearing berets with a tuft. Blue (French) or red ? (Belgian) !
As far as I could feed back, this picture (and some others from the same collection) has probably been taken in 1919 192 in the port of Calais (France); this regarding a light-house on the right part of the picture.
Naval personnel aboard whilst being scrapped could be just a after-the-war visit of French- or Belgian navy-officers.
Any other comment welcome.