Paul & C-H
I echo the question above -- What exactly did you find to be the problem with the RCBO? I've come across them occasionally and not had problems beyond those one would normally associate with an RCD. All the RCBOs I've seen have a switched neutral, by the way.

These are single width single pole devices that have a pigtail wire that goes to the neutral bus - mounted in the c/u they (invariably) did't hold in - gave up and used remote 2 pole RCDs, RCD sockets & RCD fused spurs - expensive(ish) but reliable.

Senate electrical are now selling latching RCD twin 13A outlets for UK 21 pounds, the Spurs are for some reason more expensive [Linked Image]

Chris - enlightening himself about harmonics and their effect on neutral currents in 3 phase systems - I am really out of date !