French enroute ATC speak English, as they must.
ATC at international airports must also speak English. Some of it is better than other but usually good enough. You should just avoid "conversation" because many foreign ATCOs know only the stock phrases in English.
French is necessary only if going to non-international airfields, but one cannot fly to/from those from/to the UK anyway.
For France, the most official charts are the 1:1M SIA ones.
However, the 1:500k IGN charts are much nicer to use for low level VFR flight. They unfortunately go only up to ~ 5000ft which is quite restrictive as in France one can fly to FL110 in the Class E routes and these are really useful.