Richard,
The amount of personnel on a job really does not matter, if you prefer a team rather than lone worker cleaning it makes no difference, the time quoted is the time it should take to clean, assuming that the building is a medium density/use site.
With you guessing it would take 2 hrs to clean just the offices etc, perhaps there is a large number of staff in the offices, or the offices are packed out with furniture? Again I assumed about 8 office staff, if this is not the case, apologies, and yes that would make a difference to the timings.
The job might well seem difficult to complete within that time frame at first, but after a few weeks, you will find that you get faster after getting to "know" the building, the suggested times, take this into account.
The other thing that affects the time taken to clean an area is the specification, there are three specs for cleaning - Basic/Medium & High, which area recieves which level of cleaning is determined by the client or use of that particular area. Again I assumed a medium level of cleaning would be required, you could have already decided on which service level to offer depending on the current condition of cleanliness that you observed when you surveyed the premises, this would obviously affect the timings.
Regarding the warehouse aspect of the job, big broom and hard work here, sweeping such a large area by hand is hard graft, not so much if the company/client is paying you for it, but when you are trying to make a profit as a contractor, the reverse is true, again I assumed that it is not going to be a pig sty and have loads of debris on the floor mainly because of the H & S aspect, the warehouse people must do some maintenance in between your weekly visits right? There are ways of speeding this operation up as well, but that depends on the debris encountered on site.
The thing to remember regarding costings is that you do not earn anything until you clean the building, you cant charge a prospect until they become a client, and your pricing has to be competitive and the service has to be spot on too. Experience will allow you to make the right judgement 95% of the time, the other 5% will cost you money, just like all the rest of us! None of us get it right 100% of the time lol.
Hope you find the above useful!
Regards,
Robert