1. There is a 2 part test applied to charging decisions, evidential test and a public interest. Evidential test = "Prosecutors must be satisfied that there is sufficient evidence to provide a realistic prospect of conviction against each suspect on each charge. They must consider what the defence case may be, and how it is likely to affect the prospects of conviction. A case which does not pass the evidential stage must not proceed, no matter how serious or sensitive it may be".
2. The CPS usually make charging decisions, although the police can with certain lower level offences.
3. Yes, the police and CPS will continue to progress the case as required.