I'm currently in shorts and t-shirts particularly when I walk the dogs as it's often several hours up and down hills and I get a bit warm. There have been days recently (and forecast for next week) when heavy rain had caused me to don the waterproofs however I'm out in the hills so I'm clad head to toe in very good waterproofs, you won't need to be so protected if you're going to be in London as there are plenty of places to pop in and ride out the heaviest of the rain.
For me, in London in November I would be in jeans, leather ankle length boots/shoes, a polo shirt and a light jacket. This would be enoguh to protect me from light rain and a coolish temperatures. If the weather is forecast to be unusually cold then a thicker coat would suffice, my North Face puffer jacket in this case and a pair of merino gloves.