I would like to offer some assistance to James's post, re the contract won for setting up a drug counselling service.
I am a very experienced project manager, PRINCE2 'user' and PRINCE2 and PRoject Management trainer and consultant - this does not mean that I am right in what I say, but I hope it adds some credibility to what follows.
Ok, for me your OUTCOME is the 'counselling service setup to meet your contract customer's needs (reduction in drug use of a client population').
PRINCE2 encourages to translate OUTCOMEs (the desired new situation) into measurable BENEFITS so that we can see if the OUTCOME is achieving the type, degree and scale of advantage (In PRINCE2 a BENEFIT is "a measurable advantage seen by one or more stakeholders"). For your project you should develop and agree with your contract customer what the BENEFITS are. I can imagine some (but I am no expert in your domain)...for example. Number of people in the client population not returning to drug use (could be a partial reduction), measures of other related client 'behaviours' that indicate 'betterness' (crime, job loss, sickness, domestic break-up...), a cost reduction in other areas associated with the treatment and management of drug users (GP surgery time, social benefit claims...). This is really difiicult to do...but very important. The BENEFIT mesasures should be those that the project's 'customer' will use in Business as Usual time...that is, the operational measures of service success that can be seen wll after your project finishes.
OUTPUTS - PRINCE2 sees these as the 'things' handed over the project's 'customer' at the end. So for me these would be all of the deliverables put in place to enable your service to actually operate....again, I am no expert ubut I can imagine the following: documents and procedures covering service client booking, management and discharge processes, trained service providers (staff), record keeping structures (manual and/or IT), marketing and advertising material for the service (to get clients into it), awareness products to ensure 'referers' signpost clients into the service, interfaces to other services and organisations (e.g. handoffs, data transfer), service level agreements and operating performance data capture and reporting......I use a product view of outputs...another poster suggested you develop a Work Breakdown Structure - this amounts to discovering the same thing.
As far as 'whose Business Case is it?' well both you (the organisation that your represent that tendered for the contract) and the customer (whovever asked for it) both have Business Cases...but the focus and benefits are different. In my view the key Business Case for your project is the tender...that is your organisation's Business Case is to service the contract - and I assume there is some kind of motivation to do this..is it financial (you get fees) or is it for social good (or a bit of both). Your project Customer presumably has a reason for wanting to commision this work....there rationale is not the same as yours although you both are focussing on the Outcome and measures of service performance for clients being similar if not the same.
I am not sure that this helps but I am always happy to help those trying to manage projects in the real-world.
At the end of the day PRINCE2 is only a 'framework method' and is generic. It offers some good best-practice but is an 'abstract' and for many it is does seem to be difficult to apply to a real situation.
You asked about 'when does the project end?' The most important point here is to agree with the customer HOW the end will be assessed...this is what PRINCE2 covers in its PRoject Product Description which includes amonsgt other things a definition of the key COmposition (of outputs) AND Acceptance Criteria. The last item is very important...these Acceptance Criteria are what is agreed with the project Customer that MUST be measureable at the end of the project for it to be 'ACCEPTABLE'. I would assume that the contract you have will either have Acceptance Criteria clearly stated OR some areas of acceptance that can be developed into objective Acceptance Criteria. Without these, you will never know when you have finished!!
This post is already too long so I will stop here. If you want to continue the discussion then please post back, alternatively you can drop me a request to have a chat at firstname.lastname@example.org
All the best
Graham - Adjunct Ltd - "The exeprience of change"