The Disclosure and Barring Service (which replaced the Criminal Records Bureau at the end of last year) is launching its new Update Service on 17th June 2013.
Previously called a 'Portable DBS/CRB check', job applicants will pay a fee of £13 a year, in exchange for which prospective employers can carry out a free 'update' search to check their DBS certificates remain valid / up to date. This is cheaper (and much quicker) for employers, but of course shunts the cost of DBS checks onto the employee.
There's lots of guidance, and even some powerpoint slides, on theDBS website. Alternatively, I'll be talking about DBS checks at my Employment Law MasterClass which is taking place throughout the UK during July.