Hi Tara,
Part of what the Lord Patel Prison Drug Treatment Strategy Review Group is working towards is a joint strategy for prison drug treatment across government departments and minimum standards across prisons.
That said, the 2008 drug strategy has a commitment that all prisons are to have community equivalent drug treatment available by 2011. Currently, one might consider that what is available for people in the community is the minimum that should be available in prisons. Standards for the community are set out in what is referred to as the Orange Book or "Drug Misuse and Dependence - UK Guidelines on Clinical Management" and this also contains a section on prison drug treatment.
Some of the information is also encompassed in the Integrated Drug Treatment System - more information on this can be found at http://www.nta.nhs.uk/areas/criminal_justice/integrated_drug_treatment_system_in_prisons(IDTS).aspx on the NTA website.

Also, there are a range of links and resources if you go to the Review Group tab at the top - you might find things like the background document and the draft outcomes document helpful as they provide a historical context to prison drug treatment. You can also go to http://www.pdtsrg.co.uk/resources for more information.

Hope that helps! Hopefully other people can pitch in with their perspective, particularly on where information on each prison is available or information on women's prisons.