Different availability being shown to different markets is a very common feature of airline res systems. It's why even the tools like smile67's, or ITN (when it was running) are no more than guides to what's available to the UK market.

Another thing to watch out for is that some airline systems will return different availability on a particular flight depending on the O&D of your request. For example, if you ask for N class on route A-B, you may get N9 back. But if you ask for N class on A-B-C, the A-B flight may only show N2, irrespective of what the B-C flight shows.

However, now that the European Commission has successfully cracked down on the selling of tickets originating from one EU point in other EU markets, I wouldn't be surprised if they soon start complaining about different availability being shown to different EU markets.