They are prone to be more costly, but double pole are only really necessary for certain situations such as Reg 551.6.1. Would it help with PEN faults in the street? During such faults is it not your exposed and extraneous earthed parts with potential rise relative to true earth? They are indeed more fitting for protecting circuits that have sources of generation or storage, such as solar PV, battery storage, or car to grid systems. As discussed before on previous posts theses sources can generate reverse currents to flow back to the supply, which may escape the detection of a uni-directional RCBO. It is possible that, with the way things are going, it might become a necessity to fit bi-directional RCBOs if it becomes a requirement to generate electricity at home to support the national grid. After all it is now a requirement to install an EV charger with new builds (Part S)

They are prone to be more costly, but double pole are only really necessary for certain situations such as Reg 551.6.1. Would it help with PEN faults in the street? During such faults is it not your exposed and extraneous earthed parts with potential rise relative to true earth? They are indeed more fitting for protecting circuits that have sources of generation or storage, such as solar PV, battery storage, or car to grid systems. As discussed before on previous posts theses sources can generate reverse currents to flow back to the supply, which may escape the detection of a uni-directional RCBO. It is possible that, with the way things are going, it might become a necessity to fit bi-directional RCBOs if it becomes a requirement to generate electricity at home to support the national grid. After all it is now a requirement to install an EV charger with new builds (Part S)