Maybe most OO railway enthusiasts are primarily modellers rather than collectors, preferring to concentrate on their layouts rather than amass new items as they are released? I'm not sure how this impacts the discussion, it's just an observation.
Another thing that comes to mind is that as well as the online market for second-hand model railway goods, there's the actual physical 'fairs' with real traders and heaps of goods to tempt you, for example these. I love going to these. Although I almost never find any BPT stuff, I always come away with a bunch of things for conversion projects, and even for the OO layout that I might build sometime in the dwindling number of years I have left.
Another thing that comes to mind is that as well as the online market for second-hand model railway goods, there's the actual physical 'fairs' with real traders and heaps of goods to tempt you, for example these. I love going to these. Although I almost never find any BPT stuff, I always come away with a bunch of things for conversion projects, and even for the OO layout that I might build sometime in the dwindling number of years I have left.