It is not a case of simply putting someone's details into a search engine. I'll explain the process...
Your details are uploaded and searched against the Police National Computer and ISA lists (if requested), this then comes back with potential matches. An agent then has to look at the potential matches and decide if any are a positive match. It requires a human, as offenders may try to hide thier identity to evade detection, so the matching process requires a degree of judgement. This part of the process is done by CRB and is usually complete within a few days (this is stage 1-3 on the online tracking).
Once PNC and ISA have been checked the application is run through a database called PLX. PLX contains details of people who have local intelligence about them - i.e. non conviction information, which is held locally by police forces. If there is a potential match on PLX, it goes to the relevant force - this is stage 4.
All forces record and store this information differently. In home based positions they will also check any information they hold about people you live with. When local intelligence is found, the police are required to do a risk assessment to see if it is "might be relevant" and "ought to be disclosed". Many forces are very, very slow at carrying out their local intelligence searches. Additionally, they may be deliberating about whether to release the information about someone. Some local intelligence may be things you don't know about eg you associate with known paedophiles etc.
Be aware that CRB has no power over the police andhave to wait until the police complete their searches.
I hope this helps you to understand the process :o)