Let's say 4 kids per carer, 10 hours per day, minimum wage of £12/hour, an overhead multiplier of 3 (to cover rent, maintenance, insurance, taxes, sickness cover, etc), and you get to £72 per day per child.

Or about £1,500 per month.

Now, you can increase that to 8 kids per carer with older kids, but that's really stretching things if you want to run at all smoothly.