Hi Olivia,
we recently found a nanny for our 6-months-old daughter in Fenières (near Thoiry). First, we went to the city hall (rather village hall as we live in St Jean de Gonville -- well, the "mairie" ;-) to get the list of all nannies (assistantes maternelles) located in our village. Then, we went through the list with our neighbours and acquaintances to try and get recos ... which proved very useful as there are huge differences between nannies, their ways of taking care of children, the environment (space, garden, pets,TV or not ...). After meeting two nannies we decided for the 2nd one and think to have made a good choice.
As for the Péron/Logras area I have heard of Mme Geindre, though it was through another nanny so no guarantee as to impartiality ...
wishing you all success and a wonderfull nanny for your little one !