The Sybil/Branson thing doesn´t grab me as a great love story tbh.
What was it made him "dare" to even think about "chatting her up" iyswim.
I know she supposedly doesn´t care about her place in society, the irony of that being that if she wasn´t who she was she wouldn´t be nursing in Mummy & Daddy´s convalescent home iyswim-and expected to attend dinner parties when guests are there!
So although she might not want to be a member of the aristocracy, I can´t see her wanting to be the driver´s wife either.