Thanks for your suggestions Chris, I am going to completely redo the UV mapping and textures from scratch baring your excellent suggestion in mind.
This is only getting weirder...
It seems the initial thoughts I had with the headboard I posted (though I didn't post said thoughts!) were correct: when positioned less than a certain X axis value, the text will "lock" to the same position visually. I.e. at 0.32m it displays properly, but at 0.28m is displays not only in the wrong position but also in the same position as 0.26m, 0.16m, 0.08m, etc...
Some pics illustrating the problems:
The nameplate with the X value set to 0.32m:
The nameplate with the X value set to 0.31m:
As you can see, that is NOT 0.01m of change there, it's gone all the way to the other side of the nameplate (the second picture is taken from the back, as you can see). It looks exactly the same with the X axis set to anything under 0.31m, though I haven't tried negative values - although to be fair that's a bit silly considering that that'd be even further in the wrong direction!