I have not seen the laserdisc version, unfortunately.
The film, from 1960 until its recent dvd incarnation, was left untouched and those last, lovely moments of the score which begin when Alan Young says, "He has all the time in the world", were altered. It is difficult to describe what they did but if you have by chance a VHS copy still you could compare that with the dvd. It is a subtle change and some might not notice it, but it certainly affects the final moments. Without getting too technical, and reminding you that I am not a trained musician, it appears that when they re-mixed the music track for the dvd release they cut the opening bar of that lovely "Filby's theme piece and then inserted in its place another, later bar from the piece. Simply, they were not paying close attention to the original mix when they did the re-mix.
It may seem like a small point but it takes away the "sadness" from that final music. When a re-recording of that score was done on CD back in the '80s they duplicated exactly the music as it was in the film and it was gorgeous. When they did a recent CD recording of the original soundtrack a few years ago they used the new, incorrect re-mix from the dvd. A great pity.