Harris tweed sports jacket and waistcoat, or an arran jumper, is my cold day wear, short sleeved shirt when it's hot. I have the Morgan cashmere scarf too, it's nice.
Sartorial and locally sourced!

But what about a rainproof outer layer? Might I recommend a Belstaff waxed cotton jacket (Spring/Summer) or the same in perforated leather for the colder months?