I am wondering if anyone could tell me how many BTU's it would take to cool 160cubic metres of an internet shop bearing in mind approx 30 to 40 people all using computers thankyou very much for any or all assistance lormis.

A lot of variables here, but 40 people and computers is about 13,000 BTU, add on the classic 600 BTU / m² (assuming a 2.5m ceiling) and you're in the area of 50,000 BTU.

Several small units makes sense, if you need less cooling in winter just run one or two.

I would take the advice of a local A/C installer.