Your friend's convictions are now regarded as 'spent' for most purposes so he can normally lawfully answer 'No' to questions asking whether he's ever been convicted:
http://www.lawontheweb.co.uk/rehabact.htm
However, a criminal record is for life and his convictions will always appear on a CRB check. CRB checks are generally only carried out for occupations which are exempted from the provisions of the Rehabilitation of Offenders Act. (e.g. those working with, or alongside, children or vulnerable adults - or jobs involving security or the administration of justice).
All your friend can do now is to restrict his job applications to posts which don't require CRB checks.
Chris