they are rare because very few were exported to AU and Europe....actuly I learned that they were only exported to England and not to the rest of Europe. The British were also the only ones that got the silver versions of both, UC-1 and C-1.
About the power consumption (you mentioned this on a separate thread)..700w vs 440w that you see on the Japan models and older US models....
I know of at least 4 flavors of B-1 rear panels. Japan and early US models will say 440w and all 240v models and newer US models (thinking serial number 1800+) will say 700w.
The power consumpion stated on the box varies from market to market or point in time, to cater to the local codes. It really does not matter as all B-1s will consume more than 700w if pushed, agnostic of what the box sais. As a matter of fact, at over 200w, the B-1 sucks 1kw