I want to replace my csu. I notice in my leccy box that the main supply
tails come up through the service fuse, which has a metal seal, through a
metal block of 3"x2"x2" into the digital meter and into my csu.

It looks like I'd have to break the seal to remove the fuse to allow me to
detach the main tails into the csu.

I know you probably should get permission to break the seal (they'd probably
insist on a qualified electrician to do the job + resealing - just trying to
save some money by DIY), but it appears very easy to be done.

Then in goes the new csu with rcd and I'm update with spare fuses.

Any thoughts though on this main tails/fuse seal issue would be welcomed.