DH,
The difference between a standard and an enhanced is simply that standard only checks the PNC, whereas enhanced checks local police systems also (to be honest the same information is generally held on both).
Depending on the job being applied for this will determine, how much and what information is required to be release.
i.e If you had been arrested for inappropriatly touching a child and were not convicted but were taking a teaching post then they would definatly request further information as to why the case was dropped. In this instance I find it unlikely that further information would be requested as despite the offence it is not particuarly relevant to the job role.