 The possible participants identified will be sent an information sheet giving a simple and clear outline of the proposed research. The investigator will try to obtain an au to date residential address from the PAS system in the NHS or through confirmation from the patients GP or drug worker. It will explain the purpose of the study, why they have been chosen, what taking part will involve, the potential advantages and disadvantages of taking part and that everything will be kept confidential. It will also outline who is conducting the study, how any expenses will be paid and contact details for any problemscomplaints that arise. 