I suggest you read SG Sturmeys account on british shipping, the details of which I gave you earlier. I have provided you with a summary, indicating British ports operated well below their operating capacity throughout the war, and that 80% of cargoes were handled by the west coast ports. The remaining 20%, amounting to 17 million tons per annum were handled by all the other ports in great britain, of which London was just one. London was operating well below its maximum capacity from the beginning of the war, but any loss due to its incapacitation could be absorbed by the unused capacity of other nearby ports, or more regularly, by the other transport options like rail and river traffic.
These are the facts. I cannot help you if you lack the ability to interpret the data. Its there, and its plain to see. It conclusively shows you are pursuing a red herring on this. If you need further clarification, go do some reading