There was a great clang 20 minutes ago, and I now have the 12-letters boys and the 4-word description (though there is a choice of 2 letters where 3 meets 15, I think. But, even knowing where the description comes from, and what I'm presumably looking for, the 4 other clues remain steadfastly unsolved. So only the halfpenny has dropped.
Doubtless when the other shoe drops (mixed metaphor - sorry) the 3/15 matter will resolve itself