A question for all you electricians out there - will all mcb's fit in any consumer unit or do you have to buy the same brand as the unit.

Some makes are interchangeable and others are not, so sorry, no definitive answer. Best way is to take an existing one to an electrical wholesaler to compare or look up manufacturers' data sheets on their websites.

^ what Steve says. They all fit the din rail but the height of the hole for the busbar varies, at least 4 different types.

if you need any help u2u me as ill probably be able to find an alternative breaker if your struggling to get sorted