I'm a sh-sher of those words, too (born Wales, Welsh parents, but grew up near London; speak "Received Pronunciation").

I would say "sh" in appreciate, but "s" in the middle of "appreciation", otherwise it would sound too shshy for me ! I think the choice of "to sh or not to sh" depends on the other surrounding consononants to a certain extent. I've had a quick wizz through some of my "How to Talk Proper for Thespians and Luvvies" books - haven't immediately come across an example.

How about this one to say over and over: Special Spanish Species !

Nothing to do with the "c" pronounced "sh", but here's a lovely speech exercise to spray people with:

"Whoosh ! A shoe shied by Sheila shot past Sasha's shoulder and shattered a pitcher of shoyu on a shelf. No shilly-shallying for Sasha; her eyes flashing Russian passion, she sharply shied the shoe right back so it splashed the washing, and Sheila, most efficiently with shoyu. And thus the wretched shrieker got short shrift from Sasha over her shrunk shift."

Aha ! "efficiently" - I've only ever heard that one shshd, never ssd.

- jeanie