I really like to read the strategy plan of war!
Churchill’s job as Admiralty was focus on defense of domestic and oversea, protection of fleet (commercial and army) and preparing for the incoming war. English people are good at sea and their experience and spirit of flight on water were invaluable not only in the previous wars but also in the incoming WWII. The introduction of Asdics was greatly applied to most of the fleet while weakness on air force still expose great danger on Navy safety and coastal defense.
War plan was set up. Regular ocean convoys was established from Thames and Liverpool to/from Halifax, Gibraltar and Freetown. Commercial ships were conducted quite normally and they were encourage to equip guns on board.
Scapa, which is on the north of Scotland and opposite Norway, was selected as safe base for fleets. It was far from the air base of German and its violent tides in Pentland Firth prevent the entrance of enemy fleet. This choice was proved to be effective and wise.
The episode of Escape of Polish submarine Orzel is a delightful read in this chapter!