You can wait for ages for two Off-Broadway musicals set around a road trip to arrive in London, and then both arrive at once: Violet, originally premiered in 1997 (and more recently seen in a new Broadway version in 2014), has just received its professional London premiere at the Charing Cross Theatre; and in March the 2013 musical version of the 2006 film Little Miss Sunshine will come to the Arcola.But Violet also marks another auspicious West End moment: with Caroline, or Change playing just...