I always thought that an individual (or self-employed) wasn't allowed, directly, to get a CRB check on themselves
These days the CRB check is now called a DBS check. (Disclosure and Barring Service)
Anyway, as far as I know it's still not possible to do a criminal records check on yourself.
You can however run a check on yourself by applying for a ‘basic disclosure’ (showing details of UNSPENT convictions only) from
Disclosure Scotland
(This applies to you at any UK address).
Now, do please be aware that the ACPO police certificate will also show SPENT convictions whereas that basic disclosure will not - it only shows unspent convictions under UK law.