I have not looked at the files for this game myself but if it contains both English UK and English US sound files then try (dumping the UK ones into a new folder) renaming the US ones to the UK names, so both sets of English sound files are the US version not the UK version
Prince whats his face is not a real person, totally fictional
The manual wouldn't mention regional stuff as that side is controlled by the console not the game
Yeah a couple of PAL games do struggle with NTSC modes including PAL60 but that is normal as running anything that is only intended to be ran at 50Hz only, will mess up in some form when forced to run at 60Hz (crashing, stutter & sync issues to name a few), not an issue though as you can run at either though 50Hz tends to be interlaced on the xbox, not a big deal if your TV outputs i displays as good as p displays (with component cables), not so good if it does not,saying that though depending on your dash you can force PAL50, XBMC detects the display and keeps settings per game or you can try and manually set the display type, this however does not work for some NTSC game the other way round from PAL mode (Forcing NTSC modes or PAL 60)