Yeats actually wrote "the cloths of Heaven", which means something a bit different, and sounds different too. Still, that's the folk process I suppose. But I'd advise reverting to Yeats' preferred word, "cloths". Otherwise the image of shirts and socks lying all over the place gets in the way.

Yes, "When I was one and twenty" is by A.E.Housman. It sometimes get tagged on the "The Salley Gardens" by singers, which is where the confusion might arise. It works pretty well - but the mood of the two poems is in fact subtly different. Housman's poem has a sardonic tone, and Yeatt's doesn't. And I'd see the singer in Yeats' poem as a lot older than just 22. So I think it's a good idea to have them as separate songs rather than running one into the other.