I too noticed in Mending Stuart's Leg, the real public seemed to be about, getting on with their business, while the filming went on.
Would never have happened as the series progressed.
HOWEVER, have a look at the beginning of the 1973...
There was a policeman near the road crossing in Stuart's leg, when the trio and Sid were carrying the ladder to the cafe. I wonder if he might have been a real policeman, there for crowd or traffic control?