An individual can't get a CRB check on himself. He can only give his permission for a potential employer (or for a controlling body, such as a Licensing Authority) to obtain such a check.
However an individual can seek a copy of his 'police record', which involves paying a £10 fee and providing proof of identity.
Perhaps the police are trying to work out which of those things you're seeking to do. If it's to obtain a CRB check on yourself, they'll be obliged to refuse. If it's to obtain your 'police record', they'll want proof of identity (and a tenner).
Chris