If you are on pre-charge bail and the police are aware that you have breached your conditions, they have the power to arrest. However, breaching pre-charge bail conditions is not a criminal offence in itself, unless the breach involves a separate offence such as witness intimidation or perverting the course of justice. Unlike post-charge bail breaches, there is no court procedure for pre-charge bail breaches, meaning the police handle these matters directly.
Once in custody, the police must decide whether to charge you with the original offence. If they have sufficient evidence (and CPS authorisation if required), you may be charged. If not, they can use this detention period to seek a charging decision, a further three hours is added to the detention clock when someone has been arrested for breach of bail. If a charging decision is not made, you will be released from police custody.