Just for reference here is a few images of the 3.6mm "Asian 2813-2 clone" in the Bell & Ross watches. It is exactly the same thickness as the ETA - 3.6mm, but it's definitely NOT a Seagull ST18
[img=http://img85.imageshack.us/img85/1655/cimg5943me5.th.jpg]
I can also confirm that the Seagull ST18 will not fit in any of the B&R cases, precisely because they are a clone of the ETA 2892 - the stem release is in the wrong place.
Here is an image of the ST18. "1" shows where the release button is and "2" shows where it would need to be to work in a rep B&R case.
I guess this means that I'm going to have to now buy another watch and pray to god it's one that doesn't have this thin mechanism in it, because after more than 6 months looking for a replacement and coming up with nothing I think I should finally admit defeat....even the dealer that sold me the original watch can't get it for me.
Worth thinking about in hindsight....If you want to keep your reps for years you need to make sure that the mechanism is cheap and easily replaceable.