He did not regain the Prime Minister's Office again until 1951.
Churchill did push through some temporary measures to deal with health care during the war, but it was Attlee's Administration which made them permanent and turned them into socialized medicine with the NHS.
However, it was the Beveridge Report, commissioned in 1941 by the Labour Minister Without Portfolio Arthur Greenwood, which set the stage for the NHS in 1946. Churchill did not act on the report during the war.
It should be remembered that Churchill did not head a Conservative government during World War II. He headed a national coalition government which was succeeded by Clement Attlee in 1945.