A while back I corresponded with Steve Nutter (yes, that's his name) about the project:
"TUBUP is a bonkers project that seems to be taking on a life of it's own since we started it in May last year. It seems that it's not just about kids either...adults seem to have as much fun with the project as well! We're not directly connected with Utterly Butterly, although they provide us with their reject tubs, and let us use the name. Good marketing for them I suppose! They have contributed financially to a few "one off" gigs that we've done, like Children in need Cardiff. The great thing is that the ukes actually work really well and it's fab fun!"More information, including sounds, video, and instructions for making your own margarine tub uke are at this link.