UK criminal records are not available to the public. Certain employers can carry out checks with the Criminal Records Bureau but they can usually only do so where the employment involves contact with children or vulnerable adults. Even under those circumstances, the employee (or job applicant) has to sign to give his/her permission for the check to be carried out.
Even the police can only check on criminal records when they've got good reason to do so. All checks are recorded and subject to audit. In a case reported in the press, a police officer used the police computer to check on whether his daughter's boyfriend had a criminal record. He was sacked, prosecuted and sent to prison.
So, unless you're prepared to pay a very big bribe to persuade a police officer to take a very big risk, there's no way that you can access anyone's criminal record. Anyone providing you with access to the information (either directly or via a website) would be committing a serious offence which would almost certainly lead to their imprisonment.
Chris