The Gordon Moody Association gives a list of support organisations here

GamCare has a similar list and offers advice

BeGambleAware signposts support via free counselling and phone

RethinkGambling has a support section

The NHS has a useful page including support links

Mind, the Mental Health Charity has a comprehensive site which includes information, advice and links to support. As well as links to addiction support it includes in its A-Z directory links to other places of support for issues often confronting addicts, such as debt, anxiety, depression.