I think what France has is a system where every flight plan goes into some central database and every ATC unit can access this immediately.
Also (I am told) every French ATCO is radar qualified which means they are allowed to view radar data, and they all seem to have access to radar screens. Radar units have a huge advantage because they can see you, so there is much less radio work for both sides. They can see your filed route so they know your intentions.
France seems to have gone for a "known traffic" environment and a relatively integrated ATC system, and this brings them obvious benefits.
But I also think this works in France due to the nature of their airspace and their GA activity. There is very little GA there, with a certain number of foreigners flying around the place, and with French pilots mostly doing short hops at low level, club to club, and the latter probably don't talk to ATC much.
In the southern UK, the main FIS is London Info which is staffed by non ATC personnel (FISOs) to save money, so they could not have access to radar data. This was changed some years ago (due to the vast number of CAS busts) and they can now see screens but are not allowed to say anything on the radio that indicates that they can see you.