Justcleaning,
Firstly 4 hours a night is too much for one person, pukka cleaning is hard graft!
You will also increase your costs, due to NI contributions, better 2 cleaners per night, after all most cleaning staff have a day job too, they will not knock themselves out in the evenings.
Also, you wont be in such a bind if one of them call in sick, or is on holiday.
How do you arrive at the true cost of employee's?
Try this:
1 x Cleaner paid at £7:00 per hour x 2 hours per day x 5 days per week = £70 per week wages.
1 x Cleaner is from next year entitled to 28 days holiday, so
28 x 2 hours at £7:00 per hour = £392:00 per annum divide this by 52 working weeks = £7.54 per week.
Add these two figures together which = £77.54 per week spread out over the working year, per employee.
You also have to add on the cost of the associated paperwork that goes with employing people, such as payroll costs, training, sickness cover, maternity/paternity leave(if applicable), employers liability insurance, Health & Safety, etc.etc.
Then there is the cost of chemicals, equipment, uniforms, advertising, administration, profit, etc.etc.
Hope this helps, regards,
Rob