Evacuating children out of towns and cities to the countryside. During its invasion of Poland, German bombers had attacked the cities, and there was no reason to suppose they wouldn't do the same if they attacked us. Over 7,000 children were evacuated from Bootle alone.
Identifying, requisitioning and signposting, buildings which were suited to particular aspects of war, such as empty schools for storage, or robust basements that could be used as communal air raid shelters. The likelihood of being killed or injured in a shelter was much less than outside, but shelters were occasionally hit.
Identifying spaces within homes which could be used in an air raid, such as under the stairs (The staircase effectively braces the wall making it much stronger).
Issuing family shelters, such as the "Anderson" shelter, with instructions on how to erect them.
Assembling voluntary "Civil Defence" groups, responsible for maintaining civil discipline. eg "Put that light out.", "The shelter's over there. Be quick." etc
Installing air raid equipment including:
Sirens. Fortunately, Liverpool was ahead of its time with the adoption of electricity, so this was very simple.
Anti Aircraft guns
Issuing the famously never used Gas Masks.
Bolstering fire fighting provision by the use of EWS (Emergency Water Supply) tanks and stop planks on the canal. Because the canal ran through the industrial heart of Bootle and North Liverpool, it was a valuable fire fighting resource, and so it was effectively divided up into EWS tanks at night. Air raids were invariably timed to arrive at night.
Marshalling supplies, including:
Turning industry over to "War Production". All those vehicles that came from America for D-Day came in kit car form because you could get more on a ship that way. They were assembled in a small factory on Smithdown Road, Liverpool.
Improving agricultural efficiency. Before WW2, Britains agriculture was very ineffcient, using medieval methods.
Bringing every available ocean going craft into service to ensure the supply of food and machinery to the UK from the Americas and colonies.