June Tabor.

Outside opera, you can easily argue that June Tabor has the best singing voice in the UK.
Check her out on Youtube or Spotify if you are not familiar with her voice. She covers a very wide range of musical styles in her catalogue.
I have seen her in concert three times over the last 40 years or so and must have well over 50 of her tracks in my collection.
She often performs with the brilliant, world-renowned blues guitarist Martin Simpson.