I need a 20A B-type MCB to fit an existing Legrand domestic CU. The part number is 06161 but I believe that other Legrand/Tenby MCBs will also fit. However, I'm having little luck in sourcing one, new or used. Can anyone identify any other model or make of MCB that will also fit the Legrand unit? The MCB would go at the end of the row, fed from an RCD. Failing proper busbar alignment, is it permissible to feed the alien MCB (or, alternatively, a single-module RCBO) through a wire link to the adjacent MCB/busbar? I realise that mixing makes of MCB/RCBO is considered by some to be bad practice but, if the correct item is not available, this may be unavoidable.