Anyway I don't agree with Christian - a 25 year old Wylex fusebox is
likely to be perfectly safe, assuming there's been no abuse like fitting
"uprated" fuse-wire.

Have you ever seen an unprotected wire fuse blow?

Quite frankly, I wouldn't be surprised if replacing the fuse wire with a
nail was actually safer!

Cartridge fuses are another matter. They are perfectly safe and the only
reason to change one of those for a modern unit is for convenience, or if
earth leakage protection is required and it is the simplest method to
achieve this.

Christian.