The Samaritans (08457 909090) offer a lifeline. You can email the Samaritans in confidence at firstname.lastname@example.org.
Hampshire Lanterns has been formed in liason with the award winning Hampshire Perinatal Service, details of which can be found here: http://www.southernhealth.nhs.uk/services/mental-health/adult/mother-and-baby/
The Association for Postnatal Illness (020 7386 0868) can put you in touch with trained, experienced volunteers.
PANDAS is a UK charity supporting families suffering from pre (antenatal) and postnatal mental illnesses. Their web address is: http://www.pandasfoundation.org.uk/ They have a telephone helpline open 9am to 8pm Monday-Sunday : 0843 28 98 401
Action Postpartum Psychosis – http://www.app-network.org
The British Association for Counselling and Psychotherapy (BACP) website has a search facility which you can use to find a qualified counsellor or psychotherapist in your area.
The Depression Alliance produces a leaflet and runs a helpline (0845 120 6162) for anyone affected by depression.
Home Start can visit you at home and offer friendship, support and practical help, as well as put you in touch with other parents in your area.
Mind offer information and support to anyone experiencing mental health problems.
BabyCentre have a great article on postnatal depression in dads.
Other useful links
Family Lives (0808 800 2222) is a helpline that provides support and information for parents who are under stress.
Cry-sis (08451 228 669) will put you in touch with a local supporter, for advice about excessively crying, sleepless and demanding babies and young children.
The royal college of psychiatrists has useful factsheets on various mental illnesses.