One of the problems in this sort of work is setting boundaries. If you don't set them, the museum will simply be a hodge-podge without any real focus and your scarce resources will be spread very thinly; on the other hand the chances of getting funding from any official body is likely to be better if the boundaries are quite wide. As an example of the difficulties of setting boundaries, think of the Notting Hill Carnival. It would certainly not have shown up in C#'s day so in that sense is not an "indigenous folk tradition" to London. On the other hand it is arguably indigenous to a sector of the people of London and is certainly a very well established event now for a much wider section of the population. So while I would personally include it, you can see how deciding what to include and exclude is fraught with difficuly.