Rab Vapour rise. Absolutely ruddy brilliant. I’ve barely taken mine off since I bought it.
Warmer than it should be, light, windproof, showerproof (dries quickly) very breathable. Comfy enough to wear it next to the skin as a base layer, or as a midlayer under a hardshell hardshell if it’s really cold and raining.
Knocks the spots off a “real” softshell in my opinion. The ones I’ve tried (inc a nice Noronna one I found in a sale) Aren’t as warm, light, comfy or breathable.
One option is just to combine a very light windshell and a light midlayer. They’ll do 95% of the same job, and be more versatile. And cheaper, as you’ve probably at least of those already!