Can anyone advise me on whether it is legal and safe to use RCBO's in domestic applications.
I am having trouble with RCD tripping spuriously so thought I might protect each circuit seperately with an RCBO.
Yes you can use them. There are a few places they are not allowed for example generating sets, farm building, caravan sites, Marinas and where a special type of earthing using as system called IT is used. (Nothing to do with computers) This is because in the main they do not switch off the neutral but their price is dropping my last visit to whole sales in Chester they were Â£12.5 each. There is at the moment much talk about this as RCD in some form will be required on all circuits with the new regulations. Also under new regs you are not allowed to put all circuits on the same RCD because of the problem you have so new consumer units have been made with three neutral bars and the new regulations will see at least two RCD's plus some RCDO's in every house. Comes into force July 1st.