I'm not personally aware of any set standard for ratings of panels, it is normally either whatever the consultant specifies, or manufacturers standards.
Any electrical installations must comply to IEE regs BS7671:2008 (the wiring regs) at the least. Ideally your company (or the electrician you sub it out to) would be NICEIC registered, and probably should have done his Part P given the size of jobs he does.
You can buy the regs from anywhere...
cha1n:
I'm slightly alarmed that the company you work for would just 'guess' at a suitable breaker size to protect a circuit. No-one but a trained Electrical Engineer should be doing this. By asking you to do this without training they are asking you to break the law as I see it - if there was...
