I love the clothes! Rational indeed. This made me think of my gran, who would have been about 18 0r 20 then. I don't know if she cycled but she was very adventurous and belonged to a swimming club in Southend, whose activities included night-swimming in the sea.
In some ways it must have been a very interesting time to be a young woman, with more avenues opening up to you - presumably a lot of those on the film would have been munitions or other workers who were being paid much more than they would in a life of domestic service, and had the company and conversation of their peers in a way which a housemaid would never benefit from.
Even if you did have to live in black and white...