"Roaching for example was long a primarily working class pursuit, but now it is the market place for very expensive technical products - carbon-fibre rods, etc. I don't think that means it has lost its claim to be a folk pursuit."

Really? No, not really. You'll find usable carbon fibre rods available from a tenner upwards, £30-50 for something an adult might be happy to use, say a hundred pounds for something smart. If you want a cane rod, a 'folk' one, start looking from fifteen hunded quid upwards.
Are roach common and trout posh? I'd like to know as I went worming for some native speckled brownies on our local stream and need to know whether it was folk or not.