My thinking is that the error occurred because (the aircrew did not properly cross-check the QNH, and did not look at their RadAlts*), but also because the ATC controller was speaking in two languages. It doesn't really matter what the languages were, but having to continually flip between native and words translated in their head was a big factor in this incident. Had they stayed in one language, this mis-translation would not have occurred.
Secondly, I can't remember what was said now, but if ATC gave the French QNH as "one thousand eleven" rather than "one zero one one" then this could have been another potential factor in the cock-up. I always bang on about CAP 413, but the phrases and methodology in that document have been carefully designed to avoid confusion when instructions are passed by voice over an imperfect radio link; one subject to distortion, interference, and fading. And being received on headsets in a cockpit that can itself have other audio noise and distractions. All of which means that messages are not always clearly heard; making the use of a set of very specific stock phrases vital. As soon as people start using lazy verbal short cuts then confusion can arise.
In a busy TMA, it must be very tempting to use abbreviations, especially if one has to say "unité zero unité unité" (11 syllables, and a right old mouthful), hundreds of times, rather than the much easier and shorter "mille onze" (2 syllables), but therein lies an elephant trap. If individual digits are spoken - in any language - instead of verbal shorthand, then fewer mistakes will occur.
*Perhaps also; NPAs referenced to QNH should have DHs rather than DAs, i.e. a final decision reference based on the Rad Alt, height rather than the QNH altitude? The QNH can be mis-set by the pilots or ATC as we all know, but a Rad Alt of course measures the actual height above the ground and therefore is a more reliable reference.
In fact the last 2,500' of most NPAs could be referenced to height rather than altitude, which would add a little more precision and safety.