Large room in exchange for help around the house

This is the house

We are a family with 4 children aged 10-17 living in a beautiful house overlooking Clapham Common. We are looking for someone willing to swap our large attic room (with own bathroom two floors down) for 12 hours a week helping around the house and two night's babysitting a week from 7-9. 30pm.
You need to really like children, be very neat and tidy and be happy to help with light domestic work such as hanging out laundry, cleaning the kitchen and tidying up. We are asking for 12 hours work a week and two nights babysitting which is for our younger daughters who are 10 and 12 years. This involves making sure they have had dinner, getting them upstairs to bed and checking on their homework after that you are free to go out if my older boys (aged 15 & 17) are home.
Hours would include about 45 minutes in the morning to clear away breakfast and hang out some washing and an hour on a Saturday and Sunday the rest is flexible.