You asked for my opinion of the UK film "Keep it up Downstairs." Can't give it to you, because I've seen only the spanking scene, which I have on a multi-dubbed videotape.
As far as the spanking itself goes, it is pretty to look at because of the traditional OTK positioning... but ultimately it disappoints, because all the butler does is pat the girl's bottom a few times, lightly. I realize that movie spankings have to be faked to some extent, but this one doesn't even try to look real.