I read it ages ago but googling is giving me nothing.
There was a wife called Sophie, a daughter called scarlet who was in hospital having her appendix out, Sophie's mum was called Constance and she was an actress who gave up a baby for adoption that turned out to be Sophie's husband. Sophie wrote letters to a baby she had to have aborted. Simon was having an affair with a hairdresser whose mum had once slept with Constance's husband, making the hairdresser (Della?) and Sophie half sisters.
I cannot remember what it was called and I wanted my sister to read it as we were talking about batshit interwoven life scenarios