Nice shirt!
I would be inclined to view the shirt as something akin to 'dressy jeans' in terms of Angie's "smart casual" formulas. The formula is that you'd pair nicer, better jeans with a pretty blouse, and dressier shoes etc.
Here's a link to one of my favourite "smart casual" blog posts that Angie wrote quite awhile back on the blog:
http://youlookfab.com/2008/01/.....nd-beyond/
I don't see why the slightly dressier denim Foxcroft tencel shirt wouldn't work as the 'denim piece' in a smart casual ensemble, it's just that things would be a bit reversed. The smarter-looking denim blouse/shirt you have would sub in for the better-quality dark wash jeans in Angie's formula. In this respect, you might want to pair the denim shirt/blouse with a dressier pencil skirt or perhaps slightly dressier pants. I guess what I'm saying is that I can't see why Angie's "smart casual" formula wouldn't work when it's the top that's denim instead of the bottoms?
How about the following ideas:
black tank, black high-low midi skirt, Foxcroft tencel denim shirt knotted at waist, cognac sandals/shoes etc. ?
the Foxcroft tencel denim shirt tucked into a dressier, more conservative-looking pencil skirt - ie. one of those Halogen seamed pencil skirts or perhaps one of your new Ellen Tracy Ponte skirts?
http://youlookfab.com/2010/03/.....ssy-skirt/
pairing the nicer-looking denim shirt you've just acquired with an actual suit?
using the shirt as a way to 'dress down' a fancier dress - kind of like pairing a denim or leather jacket with a fancier dress? See the below post:
http://youlookfab.com/2010/03/.....ball-gown/
dressing up the denim shirt in general:
http://youlookfab.com/2009/08/.....im-shirts/
More denim shirt ideas (love it paired with the sequined pencil skirt...wow!)
http://youlookfab.com/2010/03/.....im-shirts/
In the meantime, it looks like you scored a great shirt, and I'm sure you'll find a way to make it a real wardrobe workhorse. Fab find!