Your GP is the person to talk to if you would like to be referred to talking therapies provided by the NHS.  Unfortunately a three to six month wait is likely. 

Below is a list of organisations that are a good reliable starting point for finding a suitable therapist outside of the NHS.

 UKCP - UK Council for Psychotherapy

BACP - British Association for Counselling and Psychotherapy

London Psychotherapy Network -  I am a founder member of this new website which aims to demystify the talking therapies while providing a directory of London based practitioners.

MIND - Leading mental health charity for England and Wales

CAMHS - Child and Adolescent Mental Health Services

The Minster Centre - Integrative training organisation and low-cost therapy referral service in North West London