My house was built and wired in the 1980s and has an old-style fuse box.
The old fuses have all been repeplaced with cirquit-breakers plugged into
the fuse sockets. A couple of people, such as estate agents and
electricians have raised eyebrows on seeing the box, telling me it should
be changed for a modern RCD unit. Is this true? I've never had any problems
with the existing setup, and I rarely get any inexplicable tripping of the
circuit breakers. As far as I am aware, the old fuse boxes (even when fuses
contained fuse wire) did what they were designed to do, with no problems.

My fuse box has circuit-breakers for:
Upstairs ring main
Downstairs ring main
Upstairs light circuit
Downstairs lighting circuit
Electric shower circuit
External security lights circuit

Obviously, I'd like to avoid the expense of updating it if I'm not under
any legal obligation to change anything. Is there really a significant
increase in electrical safety with the modern RCD units?

What about if I rent the house to tenants? Will it then need to comply with
the latest electrical regulation specs?

THanks for some help.

Jim