With regard to tailors wages & social standing, it would generally depend on the type of work that person was doing.
If making clothes as an independant for middle to lower upper class clients I would say that they would have been very much within their own social class.
But if in a workshop or working for a large store then they would have been considered working or lower middle class.
Of course the girls who did this job, worked long hard hours for a pittance, in bad conditions.
My g/grandfather was tailor in the early to mid 20c. His speciality was buttonholes & he worked in Saville Row, his family lived in quite a nice part of Fulham & then moved to Clapham, so not too bad.