So in figuring out which MCB controlled a particular socket, I switched one off. It now wont switch back on despite turning off all the socket on that circuit. The consumer unit is Hager branded… and I can’t find any of the local B&Q/Wickes/Toolstation/Screfix etc.. which stocks Hager stuff.

Are MCB’s to a standard fitment – i.e can I use any brand in there as long as it’s the same type (Type B?).

Cheers

yes IIRC

No
The the busbar (the fixed copper strip) can be different sizes/height etc.
Some are compatible, some big names make them for the sheds. Hager is a good quality item and I think pretty unique.
Did you do anything before you tried to turn it back on, why were you fiddling. I ask because there might be a fault hence it not switching on.

I can get you one, but a proper wholesaler will have them. You’ll need the part number – something like MT132.

I tried anyway. The Wickes ones (branded Clipsal Powerguard) fit perfectly. The busbar just inserted straight into the bottom without any issue. Works fine now…

I was tinkering as I wanted to swap a single switched socket to a double to allow me to plug both washing machine and new dishwasher into the same outlet. Before starting I just wanted to make doubly sure I was isolating the right ring main first! Just switched off the MCB and it wouldn’t switch back on. I wasn’t getting the click to suggest it was being latched, so figured there was probably something wrong with it. With the old MCB out the switch still didn’t latch. Chatting to the neighbour and just flicking the switch on-off it started latching after a while, but not reliably every time. Guess the switching mechanism has just got tired/old/whatever…