There is a book by a fellow Brit - Jocasta Innes, called Applied Artistry, 1995. This is an excellent primer for all you ask and more. It should even be in your library system. It is showing up cheap in discount booksellers as well. Scagliola is the high quality imitation marble, stucco lustro is a form of polished or "Venetian" plaster.

Stucco Duro is even deader than fresco - there is no one in North America practising it at this time and the only examples over here are in Spanish Colonial Mexican churches. My own formula is still being adjusted, and I may choose to sell it in buckets, so it is closely gaurded.

Are you mainly a painter or a sculptor?