Thanks all. My ancestors were Charles Crossley and Mary Poynton, through their daughter Elizabeth (who had at least 4 children and never married - she didn't bring any of them up either).
The problem we have is that none of the names on the postcard match any of the Crossley cousins or even second cousins. Elizabeth had a younger sister Eleanor (Nellie) but she was older than the girls on the photo. Looking further afield, the only Rhoda we can find is Rhoda Champion (later Quarmby), who would have been a Cousin, though not strictly a "Crossley Cousin", though of course the term cousin was often used to denote more distant relationships. But even going down this line, we can't find any other names that match.
Arnold visited Rhoda (and the others?) and was in trouble for going AWOL.
It would be great if someone recognised these people. I've had it on the Sheffield, Stocksbridge and Huddersfield Forums and family history sites.