A question though guys, speaking to a few electricians locally and by no means anything special just normal leccys, I have been told that I "may" need 3 phase. Not really familiar with what this is other than they use it in industrial buildings. Is this true in order to fit the air con units id need 3 phase.
Sometimes the outdoor condenser unit will require a 3-phase supply, but this is generally only true for large units designed with the capacity to heat/cool very large areas.
As I keep saying, you really do need to involve a local A/C engineer before you start contacting electricians or any other trade, otherwise you have no idea of what type and supply size will be required, never mind anything else.
In any case, I can assure you that given the size of the premises you have described, there will certainly be single phase units available large enough for the job. It's possible you might have a 3-phase supply anyway - if you can post a picture of the service head where the supply enters the building then we'll be able to tell you.
Furthermore someone mentioned a ducting system saying that you have one unit that does everything and you have ducts running to several points in the building. Are these systems any goods as I may have a way of fishing the ducts around into appropriate locations
The ducts for these systems are large. A high static pressure unit will require ducting somewhere between 80-100mm in diameter (although AFAIK this sort of system is mainly found retrofitted in domestic installs), anything else may require 300mm upwards. Not really something that can be fished around very easily, and you'll also need a large ceiling void in which to conceal a ducted indoor unit.
However, if access is good and you do have suitable space in the ceiling, a ducted system would certainly be less obtrusive than wall mount units, but will be significantly more difficult to install. Given that your original brief was for a system that would require minimal interior work, I'd say that rules out ducted.
