How many offices, how many desks in each office, what type of equitment is there in offices, how many loo's, urinals, rest rooms, kitchens, bins, will this included screen cleaning partition glass, telephone sanitizing.
how did the previouse firm work..how many hours per week...how many staff...why do you think they failed?
How can you improve on what they did (ok make it cleaner , but how). I estimate how many man hours per visit x wages +cost of material +cost of machinery+6% for bits I may have missed + % for admin & insurance +% for profit.
Hope this helps
Petra