Well, my Season 4 set from France arrived today, and skimming through it, I'm happy with it. It's not field blended unlike the UK set, although the bonus Company Picnic episode actually does suffer from field blending this time around. Showshank have informed me that this is because it was the only source available for the episode. From what I understand, they've worked extremely hard for the inclusion of it, as it seems FOX was either difficult, or unaware of the complete episode's existence.
I'd also like to include this screenshot comparing the UK to the FR release.
With the FR release being interlaced, the "horizontal stripes" will not be apparent during playback, as DVD players are equipped with their own de-interlacing software, whilst the UK set has ghost frames forever, it is impossible to remove that without going back to the source material, which is only accessible to the studios and owners. I do however, acknowledge that the ghosting will probably not bother everyone.
So basically, this "field blending" is what causes the video to appear jerky when the camera pans, right? If this is the case and these discs don't suffer from it, I think I'll double-dip and buy the French sets, too. I'm glad to have the UK sets just to have the show, but since the French versions seem to be better, I think I might buy them. I'll probably wait for the full series box set, though. I'll pay less per season.