Only watched it a couple of years ago - see here - but a good one to end a Sunday Four (or Five, in my case).
Pictured: Leslie Manville, Ellen Thomas, Jason Isaacs, Freddie Fox, Jeremy Wheeler. Rose Williams in the wannabe actress who we probably recognise from Sanditon.
Much of Paris and London was actually filmed in Origo Studios in Budapest. The production designer Luciana Arrighi had actually been a Dior model in the 1960s so knew the world well. And Dior themselves were helpful in providing photos so that they could recreate the salon accurately. She has worked as a production designer since 1965, notably on the Merchant-Ivory films (she won an Oscar for Howard's End), also Sense and Sensibility.
The costumes (modelled here by Alba Baptista) were the work of Jenny Beavan, also Cruella, The King's Speech, Sherlock Holmes, Gosford Park, Sense and Sensibility, Remains of the Day, Howards End, Mountains of the Moon, A Room with a View.. in fact pretty much all of the Merchant-Ivory films.