Lunia: Layers are actually better, so if you have a warm sweater to wear under your light jacket, that might be the way to go.
The weather is quite changeable at the moment and is certainly getting colder. I haven't got my big coat out yet, but the wooly jumpers are now being worn with my jacket. Good tip is to have a waterproof on hand just in case you get caught by our showers! Oh and the umbrella! It's England afterall!