My feeling is that it is pre-war.....look at his breast pockets, they are a different shape to the home guard battledress pockets, his is a tunic I reckon.
I believe it is referred to as Service Dress.
His cap suggests 1930's, his tunic pre-1937? when Battle Dress was introduced.
Territorial units got all the disused kit, so a possibility if its a later photo.
Not home guard though.
Someone will be along shortly to give us the exact answer......
what do you know about him?
Pete