In the last stages of upgrading the supply to the garage/workshop.

The elec board tails (25mmsq) come into an existing 100A fuse &
isolator (mine not the board's) which then go to the house CU (about
3m away). I put in a Henley block after the isolator to split off the
garage supply. From the Henley block I put in a new 100A isolator &
63A MCB (type C) then ran 16mmsq SWA cable (3 core including earth) to
the garage. At the garage end this will go into a new 100A isolator &
then into a new split load CU.

Result is 5 queries bothering me:

A type C 63A mcb was used on the assumption that it would discriminate
against the type B MCBs in the CU (& also because TLC didn't have a or
couldn't supply a 100A MCB). Is type C correct here?

Should the old 25mmsq cable to the house CU be protected at the Henley
block end? To do that would need a 100A MCB: What's best here?
[there's no room for a bulky switch & fuse).

Is the garage end (new isolator & then CU) OK? or is further
protection needed to protect the new garage supply at the incoming
point?

The old 100A fuse & isolator at the incoming end is large. Could this
be replaced by a 100A isolator & MCB? Or some other alternative?

Can any (split load) CU be used for the garage end or does it have to
be special - weather proof etc? [BTW the garage is dry, but what do
the regs require?].

TIA for all opinions

[BTW nothing is connected yet beyond the new 100A isolator after the
Henley block]