I want to check myself
A Disclosure is not like a licence or Passport. It is a means for a 3rd party to check an individual.
The 3rd party must be offering a paid or voluntary role where the individual with be acting their behalf or with their endorsement. The 3rd party must also have the sanction of not placing or endorsing the subject if they do not consider the Disclosure to be satisfactory (within the constraints of the Code of Practice*). For Standard or Enhanced Disclosures the role must be exempted from the Rehabilitation of Offenders Act (1974) as specified in the Exceptions Order 1975.
Consequently an individual cannot apply for a Disclosure at the Standard or Enhanced level solely at their own request. (This includes directors of companies where technically the company is a separate entity+.)
If you are self-employed there are ways of obtaining a Disclosure through a trade organisation or other regulator.
As a Registered Umbrella body, DDC contracts with the 3rd party to act on their behalf to obtain the Disclosure (even though the subject actually makes the application).
Individuals who are being asked for a Criminal Record Check by an organisation that is not registered with the CRB or Disclosure Scotland can suggest that they contact DDC to act for them.
Individuals who simply wish to know what information is held on them should ask at their local police station for a Subject Access Report under the Data Protection Act. This costs £10 and takes about 6 weeks.
(*) The Code of Practice requires that users of the Disclosure Service only consider information contained in a Disclosure in the context of the role they are offering and do not unfairly penalise somebody for something that has no relevance to that role.
(+) Even though legally they are different entities, as this would result in the individual making the employment decision about themselves. The same is true of sole Principals, although they can request that a subordinate is notified of any content.