Can't help you with the price as we don't do windows, but on the parking front, you can get a day permit from Kensington & Chelsea council £44.00 per day to park on either residents bay or parking metre BUT you need to give them a minimum 5 days notice so they can get signs out to reserve the bay you need/want. We do this when we are in London, pass the cost on and saves any hassle. No congestion charge in Ken & Chelsea anymore.