Hi Daniel,
It depends on how much equipment you have to put in (safety & machines), what your paying your staff, what your overheads are (chemicals/ cloths/ insurance/ running costs)and what profit you want and of course, how much you want the job.
To be honest, you would probably get away with £20hr per person, I have overpriced many builders cleans, purely because we didn’t want the work and what happens, we end up getting it.
Andrew