Coming to terms with and managing an immunodeficiency is likely to have an emotional impact. Many people will need emotional support or professional psychological counselling at some stage.
It is always important to discuss any emotional difficulties with your GP as they will be aware of local services. Having a conversation about your mental health to a GP may be difficult but the Mental Health Foundation have developed this excellent guide to help.
In addition to NHS services there are organisations that can either advise about or directly provide emotional support.
British Association for Counselling & Psychotherapy (BACP)
This is the professional body for counsellors and psychotherapists in the UK. The Association sets, promotes and maintains standards for the counselling profession. When choosing a counsellor it is best for the person you work with to be a member of the BACP Register http://www.bacpregister.org.uk/ This gives you an assurance that they meet the standards of proficiency and ethical practice you would expect.
This link will help you find a qualified counsellor or psychotherapist close to you.