If I have time to sort out delivery, then Fusebox - I've also found Expert Electrical good on it.
For SPD installs they are hard to beat.
Stock can sometimes be variable, with one specific RCBO or breaker out of stock... But that seems to be a common theme with many of them of late.
I did discover that my local CEF actually keeps some Fusebox stuff on the shelf, although quite a limited range.
There are some good deals around on Hager too from a local wholesaler to me so I've gone that route when I can justify it.
BG seems to have the least issues of the common boards available from sheds on the spot, which is sometimes the only option - though I hate their enclosure design with massive space wastage to the right of the main switch... Similar space issues with the Schneider Electric boards from sheds.
BG AC RCBOS are also more expensive at Toolstation than I can get Type A Hager for next day from
Edwardes , so unless their ready made kits are right it's not cost effective..
I'm waiting for a job to crop up where I can try the new Click ones, though the issue will be whether they are still around in 10 years and easy to get hold of...