The Crooked Jades (of S.F.) are indeed touring Great Britain in July and they really are a must see, one of the best old-timey groups on the West Coast. Their repertoire is diverse, including excellent originals as well as trad material. If you like your folk music neat and tidy they may not be to your taste, but if you like it grungy with a bit of an edge, you'll have a lot of fun at their show. I played with their new bassist Megan for a couple of years down here in Santa Barbara (our band was called the Lemon Pickers), and she is really something. She can bow just about any fiddle tune on her bass. She used to play a version of the Fall of Richmond that was mind blowing.
Go see them and by their albums. They're even available on iTunes.