The company I am working for at the moment has a radial circuit for their
server room (Small basement)

I had to shutdown the three servers & UPS yesterday, as I was installing an
additional comms card to the UPS.

When I turned the UPS back on (Loaded with a router, 24 port switch,
firewall and a monitor) it tripped its breaker.

I then realised the breaker is only rated at 16Amp
should this be 20A (As per normal radials?)

Would this indicate all the electrics should be checked for other problems?
(There doesn't seem to be any RCD's for anything either, just 100A isolators
in the two CU's)

This is in an office, would there be any requirement for having RCD's?

Sparks...