Some folksogns become beer / lager adverts however - Tennents Caledonian used Dougie McLean's 'Caledonia' a few years ago to great effect; don't believe it was shown in England tho I think it is available on youtube -- memorable advert!

(Adam MacNaughtion's 'Jeely Piece Song/Skyscraper Wean' was used by Milanda Bread