Who can use Disclosures and what are the rules ?
An employer or regulator can ask an applicant or employee to obtain a Basic Disclosure for any role.
Higher level Standard and Enhanced Disclosures are only for roles listed in the Exceptions Order (1975) to the Rehabilitation of Offenders act (1974) and the Government chose to make their use optional for non-regulated roles (thereby avoiding the expense of "policing" them)
The categories for eligible roles are available here.
However, their intention was that any organisation that is eligible to use the service would do so.