The Ukulele Orchestra of Great Britain come highly recommended. My wife and I saw them last night in Leicester’s De Montfort Hall, and had a wonderful time. They take themselves only semi-seriously, and play a wide range of music; if you’ve never heard Blur’s Song2 played on a bank of eight massed ukuleles, your cultural education is not complete.
They play all around the world, so hopefully there’s a date near you in the next six months.