Fabrice, 16:9 in standard definition is done by stretching the pixel aspect from square to rectangular. This is sometimes referred to as anamorphic. So a squeezed image in VLC is normal. FCP is correcting it as it displays in the viewer.
TV’s that can display 16:9 stretch the image back out, so it is up to the TV display to do the stretch. If you are delivering a broadcast master, then it is most likely going to be on tape in that anamorphic aspect.
If however you want the correct aspect on a file to play on a computer or the web, then you need to export a Quicktime from FCP with the correct ratio. In PAL that means you’re exporting 1024 x 576 instead of the usual 720 x 576. As this is a very common topic here at the COW, I suggest you do a search here for anamorphic, 16:9 etc.