cell grazing method in Temperate Climate

Hi

I am trying to help a friend finding his way through cell-grazing his cattle.
We are in the south-west of france, at zero altitude or so, and it is a temperate oceanic climate. The winters are not very cold (a few days below zero celsius) but there is a lot of rain here.
He has 55 heads of cows (som for milk, some for meat and some for calving) and 45 hectares or pasture available.
Can you point me to the right method for this situation (return period, grazin period, size of cells, etc.) ?

Thanks a lot !
Louis