Anyway since it seems to be of particular interest here is a further update to illustrate my negative findings (reported in the Round-Up in December 2013) which came after viewing the two Are You Being Served episodes to check if same woman who appeared in the sketch could be spotted, which would have been strongly supportive of her being Robina Gauge who is logged on the BBC Motion Gallery records as having appeared in both these AYBS episodes as well as the episode of the Not The Nine O'Clock News featuring the "Baby on the Bus" episode.
The following collages show the people seen on screen who had non-speaking parts and were not shown in the end credits. At the bottom of each collage is a reminder of the "Baby on the Bus" actress
Mrs Slocombe, Senior Person
(This episode had very few extras)
(There were more extras in this one so two collages are required)
The extra in the middle is the lift operator about to give Captain Peacock a kiss
The extra on the right in the green top is watching the boxing match with Young Mr Grace and his (credited) nurse and secretary - she looks a bit like Penelope Wilton.
So as I say it's difficult to correlate any of the actresses as appearing in both episodes or any of them closely matching the Baby on the Bus actress.