Any CRB check, whether at 'standard' or 'enhanced' level, currently shows all convictions and cautions, irrespective of whether they're 'spent'. (The CRB is working on the introduction of a 'basic' CRB check, which won't disclose spent convictions, but that doesn't affect you).
Additionally, an enhanced CRB check will show any additional information which a senior police officer (or other relevant body, such as 'social services' or the Department for Children, Schools and Families) deems to be relevant.
For example, I know of a teacher who found that her enhanced CRB check showed that her husband had been convicted of downloading child porn. Also, someone posted here on AB to say that his CRB check had shown that he'd been accused of grooming a child for sex, even though such allegations had never been put to him by the police or by anyone else.
The enquiry into the Soham murders severely criticised the police for failing to ensure that Ian Huntley's enhanced CRB check showed that he'd been questioned about (but never convicted of) several sexual offences. Since then the police (and other relevant agencies) have tried to ensure that all allegations of misconduct are now included when an enhanced CRB check is carried out. While there's obviously some sense to this approach it does mean that hundreds of totally innocent people lose their careers each year through false allegations or through the misinterpretation of innocent actions.
Chris