Every job is different and has to be priced against a wide criteria, eg, furnished/empty/
lightly soiled/heavily soiled,quality of carpets, unimpeded /impeded,type of carpets.
I've done a great deal of this type of work over the years and found out, that it's essential, you see every job and discus the actual requirements with the house cleaner, as standards and expectations will not be the same and remember...........
House cleaners usually hire staff at around seven pounds / hour which is a bit less than c/c's work for.
Based on size alone and an expected time of 5-6 hours ( unimpeded ) you should expect a decent standard of cleaning, for anwhere between one hundred and eighty to three hundred and sixty pounds. Possibly more !
rob m