Hi,
I can recommend you look into a private medical practice: Wilbraham Place Practice just off Sloane Street. They have great counsellors/psychotherapists/psychologists who specialize in marital issues, also there is a lady who works there: Annie Reed Henderson who specializes in birth/child issues as well as couple counselling.
Do give them a call and ask to speak to Marianne who is the Practice Manager and can point you in the right direction.
They are very discreet and highly confidential.
Good luck!