I think Wally was easy to pick out by his size and the way he spoke, I think it was the same for Compo. I do like First of the Summer Wine I thought it was done very well, they all knew war was coming but carried on with their...
For me, the tone was a bit ominous because we were given the date at the start of each episode as a reminder that war was coming closer and closer. That added a sense of desperation to the normal adolescent social fumbling.
Given how prohibitively expensive that show was in terms of "aging" the background, I wouldn't have expected them to eliminate the cables just for a photo, although they could possibly have been edited out.
The early ones with valves probably were the worst!
I heard about someone's family getting one as a hand me down from a richer relative, but their Dad didn't like the smell of dust burning on the valves so as soon as they could afford...