Nice jacket, Tobs.
What to wear with it?
Well... here's a nice point of reference:
Contrast it with a dark knit (navy, brown, dark green) and a oxford-cloth shirt, maybe one with light, pencil-thin blue stripes on a white ground.
Linen, cotton or gummy madder silk for a PS.
Dark chinos as well (navy, dark brown, gray).
Nothing wrong with denims and no-tie in my opinion.