a cost of a nanny depends on a few things
on the area (more in london/kent) then where you are
on age of nanny, how much experince she has and if qualified
on if you employ a nanny who is a mum as well ( you can often employ a nanny mum fot less) - might be more nannies about who fall in this catrogrey(sp) as you dont want full days
25hrs a week at say £8ph I would have thought would be the right amount, as your hours may mean a nanny would find it hard to fit in another job round them