advice line (10-6 Monday to Friday): 0207 729 9904
Emergency help line (at all other times): 0207 603 8654

Release are a long established organisation offering excellent information and help in dealing with the police and courts if you get in trouble for drugs offences. The newly overhauled site has detailed information on your rights on arrest: click on the link for "bust card"

http://www.release.org.uk/