The traditional nominal voltages are
France 220/380V and I think most of mainland Europe
UK 240/415V both are 50Hz.
These are being harmonised to 230/400V due to be complete by 2008 by then all countries should have 230/400 +-10% after this the tolerance will be tightened.
French sockets have a pin for the earth and sockets for the L & N. If I remember rightly some sockets have no earth pin.
The adaptors I have (UK Plugs to French Sockets) allow for the earth connection to be made.
Having said that most appliaces I use in France are douple insulated with no earth connection so it is years since I looked.
Hope this helps
John