The British are much better at tracking sales than their American counterparts. A story like this wouldn't get anywhere in America because record companies are more creative about stealing from artists than any of their counterparts in the world (and, let's face it, record companies don't really matter anymore).
Feeder have tried to reach out to their fans, and they have been rewarded with dismal sales. The problem, I suspect, is that people don't own cassette players anymore and they're not being made anymore, either. How do you even manufacture these things anymore?
Don't confuse the cassette with vinyl, by the way. Vinyl is forever.