Attlee and Labor were attacking Churchill's relationship with Lord Beaverbrook, an Anglo-Canadian businessman and confidante of Churchill. He was quite conservative and rather unpopular due to a reputation for sharp elbows when he was in the government. So, I take it the point of removing the mask only to see the same face is to show that Churchill is not a mouthpiece for Beaverbrook. The cartoonist, Butterworth, often took on the Labour government after the war.
The second cartoon is a little harder for this American to figure out, but it seems to be saying Britain would do just fine at the upcoming Potsdam conference of the Big Three because the Americans and Russians would still respect Britain in light of Churchill's stature and reputation during the War. In fact Churchill was opening the conference with Attlee as an observer because the election results would not be known until after the conference convened.
Everyone expected the electorate would return the Tories to power because of Churchill's immense reputation, even most senior Labour politicians. Attlee himself wanted to keep the coalition government to VJ Day but his hand was forced by the party apparatus and trade unions.
It's easy with 20-20 hindsight to see what happened. The electorate was focusing on peace, not war. During the war the Beveridge Report was issued that called for the establishment of a welfare state and Labour promised full implementation. The fact was the Tories had not done a very good job on domestic policy in the 1930's and were still blamed for Chamberlain botching the job of handling Hitler. So, a country where Churchill was extremely popular as a war leader tapped Labour to lead the peace.
It should also be noted that the Tories have been in power since 1931, the Parliament disssolved in 1945 was elected in 1935. After 14 years in office most Governments are going to get tossed.