o Economy 7 is quite a bit more expensive during the day than night
---- enough that it may actually work out more expensive overall
o The meter is insufficient for the existing load
---- it could well be very old too - and miss-reading isn't unheard of

Economy 7 is typically favoured for storage heaters and such like.

You have 20 PCs & 4 Servers...
o Hopefully distributed across more than 1 RCD
---- ie, RCBOs would be good here - Memshield look attractive (as RCBOs go :-)
o Yes, earth leakage is relatively low per modern PC
---- however on 24 machines that could add up to sizeable total leakage
---- a 30ma RCD will trip at around 15-30ma

So the whole wiring installation beyond meter could do with checking,
and usual check on Earth bonding for any office kitchen & services etc.

I prefer HVAC for people & a good heat removal system for the machine room,
since 4 servers is hardly a particularly oversized load (unless they plan on more).
--
Dorothy Bradbury