Offences leading to conditional discharges become 'spent' for most purposes after one year (or when the order expires, if longer). That means that you can lawfully answer 'No' to any questions asking if you've ever had any criminal convictions after the end of that period. (The only exception is when applying for employment within occupations which are exempted from the Rehabilitation of Offenders Act, such as working with or alongside children or vulnerable adults, or working in the 'administration of justice').
The vast majority of employers have no access to CRB checks. However, if any check is carried out (at either 'standard' or 'enhanced' level) ALL convictions will ALWAYS be shown. (i.e. a criminal record is for life).
http://www.nacro.org....cro-2007021302-65.pdf
Chris