Upgrade lighting MCBs to RCBOs - no 2 way on stairs

[SW1970]

Hi folks, client has asked for upgrade of MCBs to RCBOs on split board to bring up to speed. Upstairs and downstairs lighting currently unprotected and there's no 2 way on the stairs. If I upgrade to RCBO, is there a reg that I need to refer to about the absence of a 2 way? They don't want one put in either. Many thanks, SW

 

[yellowvanman]

No reg covers 2 way switching. If you're putting in RCBOs then you're improving the situation.