Any individual can get a
Basic Criminal Record check on-line through
Disclosure Scotland.
Whilst not free (£20) it is available to anyone with a UK address and does not show 'spent' convictions.
You can also obtain a copy of all convictions recorded on the Police National Computer by application to your nearest Police Station. It takes up to 40 days and costs £10 per person. Download forms from the web site of your local Police authority.
I should add the info. available is that which applies to the applicant only (you have to give ID proofs).