Thanks again for all of your help.
The screenshot is from a WW1 Military record for the eldest son in the photograph - Individuals entitled to the Victory medal/British War medal, the page is date stamped Hounslow 1920. Could it be that he was in a reserve battalion of the East Surrey Regiment, hence the uniform being in that style?
Thanks again for your skills in putting ages to these people, it's really helping me in trying to piece everything together!