Henrys are a good bet, I have them on all sites, you will need uprights for certain carpets and the karcher or other pro types are best as they take a good hammering. Belive me your staff will abuse the tools because they dont have to pay for them, pulled leads, broken heads etc......only the best will do, dysons are good for house duty but I dont believe are robust enough for industry, ( sorry James!).
Best of luck
H