A person is unable to obtain a CRB check on themseves in the UK. The only possible way is either an expense via an agency, usually around £40 - £60 or by a Data Subject Access Request (DSAR or SAR) to the Police HQ in the area you live (costs £10)

Be aware with a SAR that this will contain every thing that the police hold on you including non criminal visits to your home and any arrests whether or not you have been charged, motoring tickets, parking tickets and cautions with the exception of the details of reasons for the penalties.

Example if you have been convicted to theft and sent to prison for 3 months your SAR will show as 1 x 3 months jail. You will then need to explain why