www.disclosurescotland.co.uk are the body for the UK who can provide criminal records checks.
basic disclosure costs �20 (which is the only report you can get without an employer sponsor - bear in mind these are usually used to check the suitability of people for jobs working with children, sensitive info etc) will give you a list of unspent convictions under the ROA act 1974.
You request an app form from them. Fill in the relevent bits. Send it back with your payment and they send you a report.
If you live in the Metropolitan Police area you can download this form: http://www.met.police.uk/dataprotection/forms/ 3019b_rev.pdf
Complete and post it, with a cheque for �10.00 and your passport (or other acceptable ID) to the address on the form
If you live outside the Met's area, you can still use the same form. Make your cheque payable to your local police force and send the form (plus your passport or other ID) to their HQ.