I've got the Sombrio one.
And also the older Scott Roarban ones.
The Sombrio isn't particularly tech. Not very breathable or windproof, but it is comfy and I like it for uplifts.
At least is doesn't have the 'cotton kills' aspect.
The older Scott Roarban ones are superb. Not a very nice feeling fabric (feels very synthetic and snaggs easily), but they are lightweight, windproof and a bit breathable. The short sleeve ones get used instead of a gillet on many rides.
And (obviously) they all show that I've been to Whistler bro.
On a positive note, a quick Google found a wholesaler/printer who can do the same t-shirts as the OP, with a full colour digital print of your choosing, for under £20 - so if you want an ethical T with a print you actually like it should be fairly cheap/painless! They also do polyester wicking t-shirts for sports - not really clued up on the eco-credentials of polyester, but this particular brand has the same WRAP certification OP mentions on his site.