Hey Azza,
I remember reading in another magazine about a couple of families that arranged to share a nanny, they agreed on a the house the children would be looked after and the nanny had 3 kids in total, the parents shared the cost.
I do remember them saying it's important they other parents you share care with have similar parenting style to you so you limit any issues.
These particular people had a Nanny through Porse.
Good luck