Hi jasper
I think you want to set up a 'social enterprise' which is a business, so you should approach this from a business perspective. You need a proposition, marketing plan and business case. The background of your employees is a matter for you although there are some interesting thoughts to be had on the ethical considerations of using disabled employees as a marketing tool which is something you will find your own way with and there are like-minded folk to discuss this with.
Once you have your proposition you will need to decide what form the business will take and you may opt to register as a charity. See www.businesslink.gov.uk (then starting up) for more info on company structures - look out for the social enterprise section which is where I think you need to be
http://www.businesslink.gov.uk/bdotg/action/la yer?r.l1=1073858805&topicId=1077475650&r.lc=en &r.l2=1073859131&r.s=tl There are also links to other organisations with social objectives embedded in ther strategy, who will have a better grasp on what youre trying to do.
Good luck