"81% of clients were opiates users, of which two thirds reported adjunctive crack cocaine use. The majority of remaining drug users were in treatment for powder cocaine (5%), cannabis (8%) or crack cocaine (3%) problems (excluding those also citing opiates). Among those aged 18 and over, opiates users in treatment had an average (median) age of 36, while adults in treatment for cocaine had a much lower average (median) age of 29 and those in treatment for cannabis use had an average (median) age of 26. Adults in treatment for benzodiazepines had the same median age as opiates users (36)."

Source

National Treatment Agency for Substance Misuse, "Statistics from the National Drug Treatment Monitoring System (NDTMS) 1 April 2011– 31 March 2012, Vol. 1: The Numbers" (Manchester, England: National Drug Evidence Centre, 4th October 2012), p. 8.
http://www.nta.nhs.uk/uploads…