The folklore of folklore is likely to be a controversial topic - as seen by the defenders of the invented 'Jack in the Green' at Hastings, Gardnerian 'wiccanism' and the equally artificial Gorsedd stone traditions of Wales and tartan romanticism of Scotland.
The problem lies with drawing a line to separate invented traditions (in Hobsbawm's sense) and real folk traditions; to say what is bogus and what is not.
His own definition of invented traditions would seem to fit much of what we happily accept as folk custom today:
"'Invented tradition' is taken to mean a set of practices, normally governed by overtly or tacitly accepted rules and of a ritual or symbolic nature, which seek to inculcate certain values and norms of behaviour by repetition, which automatically implies continuity with the past. In fact, where possible, they normally attempt to establish continuity with a suitable historic past....
However, insofar as there is such reference to a historic past, the peculiarity of 'invented' traditions is that the continuity with it is largely fictitious. In short, they are responses to novel situations which take the form of reference to old situations, or which establish their own past by quasi-obligatory repetition."
Sadly a Museum of British Folklore is likely to appeal most to those most in thrall to the bogus and invented; to the plastic pagans and the sort of Sealed Knot types who dress in upholstery brocade. It's a bubble that will need to be pricked if the venture is to have credibility, however.