Mrs. Higgins (Miriam Karlin) picks up a copy of the News of the World newspaper, indicating that it is a Sunday. However, offices and shops are open, which would not have been the case in early-1960s Britain.
Mr Ryder's car has a telephone. While a car telephone service was launched in the UK in 1961, it wasn't available in London until 1965 when base station transmitters were installed at the new Post Office Tower.
When Mrs Cragg is talking to Mr Ryder in his office (at 22 min), he asks if she lives in Pitt Street. She replies "Yes, I do" but her lips don't move.