Terrestrial French TV (and apparently some satellite) uses the SECAM colour transmission system, used only by France and some of its ex colonies in North Africa. It was also used in East Germany to prevent the folk there from watching TV from outside.
The civilised world uses PAL, of which there are several variants, the main ones being I, B and G, the difference being, as someone has said, the bandwidth separation between the audio and video transmission.
A UK TV will work in France but will not be able to correctly receive French broadcasts, which is actually a benefit. It will work on Freesat, Sky, and for DVD's etc (but not French DVDs) exactly as in UK.