This is a forum which helped me when I started my first commercial cleaning business in 2003 and I feel kind of honour bound to assist when I can although much of what Dave said amused me because of its underlying truth. I'm aware that when I help out potential competitors that it's not perfect business sense but I balance that by reasoning that ten or more additional companies aren't really going to affect me that much and will ensure that I keep my competitive edge.
So....
Everyone gets 28 days holiday a year, the basis upon which you based your fairly accurate calculation of holiday cost - no argument there. However, unless you're providing a service at a unit which is open on Bank Holidays, in which case you'd apply a premium, you are actually going to be paying four weeks holiday cover only in respect of your cleaner. Ergo..
6x8x5 = 240 (x52) = 12480 NB not 52.14 since cleaners are paid in weekly increments
Holiday Cover 4x240 = 960 : (12480 +960) x1.25 (NI) = 15 120
Chargeable 9x8x5 = 360 (x52) = 18720
These are examples only, naturally, and a job with six part time people is unlikely to have anywhere near the NI requirement above.
Also, I've never heard of a cleaning company which pays travelling time to staff. I have to pay supervisors and managers to travel between sites but a cleaner who has a contract to clean two hours a day will be paid two hours a day.
Your posts gave me some pause for thought and I'm driven to the conclusion that your experience must be in the domestic environment. My background in commercial cleaning is depressingly robust ( I wish I'd written a book instead
) and I've never heard of any company, private or public sector, which pays for travel time.
Right, back to my own problems now - I still have a fox, a chicken and a bag of corn to get over this lake and I can only fit one of them in the boat with me....