In d12dozr's example above, when unfolding and combining the hut to create the UV sheet, you create a copy. This becomes a separate object and doesn't link to the materials on the original. So, the missing step is taking the new UV sheet and re-mapping it to each face of the original hut, correct?
(seems kinda obvious, but I wanted to call out this missing bit)
In my last post above, I give a link to a tutorial by Colonel Klink where he describes how to link materials to the original component. It works but is labor-intensive and not something you could do on a hi-poly model. Here is the link: http://www.resentmentpublications.com/downloads/SUUVMAP.pdf
