Steve,
From the home page at https://sussextraditions.org/ there is a link to News & Events and I try to remember to put up new additions to the database there. Of course little or no events at the moments and the news is likely to be additions to the database.
Recently uploaded are the individual pages of Michael Blann's manuscript song book which are likely to be of interest to you, but at the moment our search machine is having problems showing the individual pages (at least using Firefox as I do). I will let you know when this is sorted.
Otherwise the serendipitous use of the search engine always reveals some neglected gems which you might consider "unusual or rare".