Marie Slocombe (1912?1995) founded the BBC Sound Archive in 1936. Her keen interest in audio recordings and folk music have made her legacy important in the history of recorded sound. You can read a full and interesting biography of her in Wikipedia at https://en.wikipedia.org/wiki/Marie_Slocombe.
As far as some of the actual song collectors were involved, stories that I have heard tell that she was something of a mixed blessing. Her thoroughness as an archivist was unquestionable but some say that she was rather rigid and regarded the BBC Archives as something of a personal fiefdom. Nevertheless the article she wrote reproduced on the web at https://pdfs.semanticscholar.org/1d4a/599177b5c746c17fe13878b0b03b8cd13452.pdf is, I would say, an essential introduction to anyone who would like to participate in this thread (though it is quite long). Unlike some .pdf files (and I don't know why) it seems to be possible to cut'n'paste from this article which may be useful to participators backing up their statements. Below I quote the 1st and 3rd paragraphs of the article to give a flavour of what she is informing us about:-

(Paragraph 1)

In a sense I write under false pretences because the BBC possesses no special archives devoted to folk music. For the purposes of broadcasting, the BBC began to make recordings at the end of 1931 and over the last thirty years has built up a general Sound Archives of some 30,000 accession numbers: recordings mainly selected from its own broadcast programmes, ranging from variety to grand opera, from the squeak of a door to full-length radio drama, from the noisy actuality of war commentaries to the stately sonority of Coronation ceremonies.

The BBC department responsible for the Sound Archives has always considered the recording and preservation of folk music, custom and dialect as an important part of its assignment, a point of view that has received every encouragement from the BBC management.
..
Extensive field operations were not undertaken until the advent of portable tape recorders in the 1950's. In earlier years, field recording, although increasingly carried out by the BBC for
documentary programmes, involved heavy recording vans and a technical team. This was unduly expensive and the outfit as a whole was cumbersome and unsuited to the needs of the folk music collector, who needs to make his approach with the minimum noise and fuss.