As someone jumping regularly between -20 and +30 (check my location ), I'd say why do you need the coat in London? Your meetings would be indoor activities. You'd go to those meetings and the airport in a heated cab. You'll drive home in a car. Where will you need the coat?

(I have done both ways - dragging the poor coat around in Arabia and also arriving to mid-winter HEL in a linen summer jacket. I prefer the latter these days)