To me, it looks like it was originally widescreen, then cut to 4:3, then smooshed into widescreen...Or is it supposed to look like that?
(e.g. the characters seems smooshed together, making them look fatter, and sometimes text or scenes are cut off, but it is displayed with black bars, top and bottom).
I haven't seen the Sundance version, so I've no idea what it's like. The UK version is widescreen. From what you describe, however, the Sundance version may be in the correct A/R; it's not as if these characters are anatomically proportional or anything.
The main difference, as you may already know, between the Sundance version and the UK is that Sundance wasn't able to get the rights to the music originally used. So no Goldfrapp, no Boards of Canada, no Black Box Recorder.