So after some searching on the internet I found a good answer to my query - it appeared that I had turned the material inside out once too often. So having unpicked the 5 wrong seams, they have been redone properly and the waistcoats are all turned right way out!
I've made 2 so that I can offer a spare to the nursery and because they're lined, they're reversible too. Aha!
Zachary came home last week and asked whether he was allowed to wear eye make-up as a moustache for the concert - brilliant! (as long as I don't have to apply it anyway!)