Hello, on most modern TVs you should be able to go into the on screen menu and change the set up from PAL to SECAM, this should enable your tuner to find the French channels. We brought an English TV over last month and this worked for us. Good luck!
Doesn't the tele has an HDMI-input? My previous TV-set was connected to the TNT-box by means of a HDMI-cable, no scart / peritel or whatsoever needed.
and there is no other input hole? Are you sure it's not hidden under a flap somewhere?