I've just bought some miniature RCBOs to replace MCBs in my CU - the
lighting circuits are on a 100mA RCD as is a spur to a socket in the
loft(!).

In a c. 1990 CU there isn't space for full-size RCBOs whereas the minis will
fit.
What I can't find out is if there's any disadvantage to a mini over a
full-sized one. So far as I can see there are some advantages:
tend to be cheaper
fit in the CU
effectively double pole
don't need to be disconnected when running tests

What am I missing on this? What's the point of big RCBOs?
--
Peter.
The gods will stay away
whilst religions hold sway