Ady,
We have a contracting division to our business and each job is quoted based on a variety of factors including condition of floor, need to move furniture / obstacles, size / type / numbers of machines required to do the job etc.
Also, considering the type and quantity of chemicals required e.g. floor stripper and polish, the number of pads you might use, number of staff etc etc...
Anyway, we average around £5 per square metre and generally get it.
Hope this helps.
Simon