I'd go for Danny Thompson; saw him with Richard Thompson a little while ago, and he was outstanding. In the folk world; Vicki Swann? Well known as a piper, but was Principal Solo Double Bass at the Royal College of Music. Not bad, then...
Anyone who wants to hear a really good, versatile double bass player 'up close and personal', drop in to the Wilkes Head in Leek any Monday night, and listen to Justin 'two string' Twigg. That guy is wasted on us...
Tim