Roughly how much is it going to cost me to have 5 x double sockets fitted into my new office?
Building is currently an empty brick stable but with an existing power supply complete with consumer unit and single socket (in wrong place).

How are the cables run, and are the sockets to be surface mounted, or chiselled in?
Type of sockets – plain white/fancy chrome? Metal clad industrial style?

A rough guess, with surface mount cabling/trunking and plain white sockets, around £200.
Chiselling out and making good takes a lot longer, so £300ish.Add extra for fancy sockets, and RCD/RCBO protection. Your bonding will need to be checked, and if necessary upgraded, most places have it already.
You need to have the sockets RCD protected – have you got that?

Surface mount – there’s going to be insulation/plasterboard fitted afterwards so no making good required. White sockets and everything should be good as our solar pv inverter is in the same room and the CU was replaced as part of the installation 3 years ago so I would expect rcd protection.

Anyway, £2-300 sounds OK.