I know the style aren't everyone's cup of tea but here are the pants I am referring too (from the BB website) Warning: Spoiler! (Click to show)
Curious if many still favor such heavy trousers for suiting...
I have a heavyweight tweed three-piece suit that I wear in what passes for winter in Northern California. The trousers are even fully lined, because, y'know, scratchy tweed against bare skin just ain't happening. The surprising thing is how breathable the trousers are. That's the only explanation I have for how they remain comfortable in a surprising range of temperatures. They're certainly warm when it's chilly out (and I've worn them in the UK in winter), but they are comfortable in quite temperate situations.
Your experience may vary, of course.