There is a bug here, because I also noticed, just as joe davis, that rebinding kp_7/Home REQUIRES manual editing (deleting) of the HOME entries in keys.cfg (a file you are warned not to edit manually...)
All other keys I tried work well with a simple rebind, but KP_7 needs to be manually nuked from the cfg file before your own new setting will "take". That is broken behavior.
PS
http://ufoai.ninex.info/wiki/index.php/Change_binding is horribly out of date to the point of the instructions not working at all.
BTW I use the following custom keys that I believe (with numlock off) is quite a bit saner default than what the game has now. Whom to talk to for trying to get something like this to be the default?
// manually rem the 2+2 openradar lines from keys.cfg before next restart of the game.
bindbattle KP_HOME "+turnleft"
bindbattle KP_PGUP "+turnright"
bindbattle KP_END "+turndown"
bindbattle KP_PGDN "+turnup"
bindbattle KP_INS "+zoomin"
bindbattle KP_DEL "+zoomout"
bindbattle KP_PLUS "levelup"
bindbattle KP_MINUS "leveldown"
bindbattle KP_ENTER "actor_next"
bindbattle KP_SLASH "actor_nextalien"
bindui KP_5 "hud.openradar"
bindui KP_5 "althud.openradar"
bindui KP_5 "radarwindow.closeradar"
//* kp * not usable currently
bindbattle UPARROW "+shiftup"
bindbattle DOWNARROW "+shiftdown"
bindbattle RIGHTARROW "+shiftright"
bindbattle LEFTARROW "+shiftleft"