I have a Barbour one made with Ventile fabric. It's my go to coat if it's absolutely lashing down. Have a wax one as well and can't say I've noticed me sweating in it but I have in my lightweight waterproofs, even the ones that are meant to be breathable.I would buy a coat made from Ventile - that's the fabric, not a brand/manufacturer.
It's a great fabric, waterproof, breathable, so you don't sweat like one made from Goretex or some of the Mackintosh ones. I find the trouble with a Barbour is that it can make you sweat a bit and the wax coating can smell a bit too strongly for my liking.