Oh, what the heck, if only so as not to be criticized as unhelpful, I'll suggest brown wool pants, an ecru shirt, and a green tie. All solid colors, since the jacket's got pattern enough, all by itself.
These colors could work pretty much year 'round (particularly if you vary the shade of green represented by the tie). I chose ecru, rather than white, because the color will do everything white could do in this combination, while bringing along some minor advantages of its own - for example, some complexions which can look washed out next to a white shirt, fare better next to ecru. Besides, anybody can pull a white shirt out of the closet; ecru is at least a little less commonly seen (for all that it's hardly an exotic shirt color choice).
Let me add that I think making the ecru shirt an OCBD, and the green tie a bow tie (wool in the winter, silk or cotton in the summer), would be a fine option.
As for the brown pants, I'm well aware of the "no brown in the city" rule (which has only limited validity, in any case). But to whatever extent one chooses to honor it, it's largely a rule involving conservative business attire. Your sport coat is, itself, a rather casual item. Therefore, one has no cause to criticize the wearing of brown pants with it as impairing its formality, or rendering it insufficiently formal for business wear. (Fine, if you're still not convinced, just don't wear the brown pants with this sport coat if you're conducting business in London. Problem solved.)
I'd wear a white linen pocket square with it. And burgundy loafers (simply because I like loafers). And probably one of my yellow (gold) wristwatches, rather than a white metal one. But I readily concede that the wristwatch thing is more of a personal choice of mine, than it is some rule of proper accessorizing. And a pair of yellow and red over-the-calf argyle socks.
If I were wearing the outfit described, and were going to be wearing sunglasses, I'd grab my faux tortoise shell Ray Ban Clubmasters.
There. That detailed enough for you?