You can be arrested without being charged of a crime. Only when the Police think they have a good chance of a case are you then charged. Once charged you either get, or are refused Bail, conditional or otherwise, depending on circumstances.
Only when the CPS decide there is a Case are you prosecuted, and a Trial arranged. Once prosecuted and sent before the judge and maybe jury you are either convicted or acquitted.
From start to finish you are treated as not guilty until proved otherwise by UK Laws.