Re 80A fuse...
- Tail size can force a derating
- Not uncommon to replace 100A by 80A these days

Condition of some networks might not disconnect a 100A fuse due to Ze
drift, so the DNO are fitting 80A fuse as a lot cheaper than
maintenance which is typically fixed-fee min-bid and repair not
replace. Like the daft "dig a road up 50x to replace 50 gas leaks
rather than mole a new pipe in once". If you "paid" for a 100A fuse
upgrade I'm not sure what they would do, probably check Ze at that
point in time.

Re radio teleswitches...
- AFAIK they did not follow summer/wintertime adjustment
- So E7 ended at 7:30am in winter, but became 8:30am in summer re BST