Sean I am not an electrical expert. However, firstly are you taking over the whole building? Do you know what the supply is to each floor? Have you ascertained what your requirements are on each floor? When you say the landlord will give you some of his supply - is the necessary hardware in place or will you have to foot the bill (usually expensive)? It sounds like you need the assistance of an electrical consultant to look over the building, the supply and your consumption needs.

sean, You have had some good advice, though I doubt that you will find many small electrical contractors with the competence to advise on large scale commercial developments. The landlord "should" be having a PIR done before you move in, the results of which "should" really be made available to you for your liability. Mind if you are not moving in until after 1/1/12 then you will need and EICR not a PIR. You will probably need a consultant, and to be honest the information that you have given, and not necessarily your fault is not sufficient to give firm advice. There are a few questions following that will help to formulate some ideas, which in the end may help. You have 1MVA available, will you be taking the full occupancy? What of the landlords supply will he be giving you? How is the internal distribution set up? Are the 2x500kVA transformers on side? What is the available capacity per floor? What are the installed circuits on each floor?

Many thanks to you all for your help.