How much did the Second World War affect Britain's economy?
WWII had a tremendous impact on Great Britain's economy. The economy had been run for years with the sole goal of war production. In addition, it had depended heavily on aid from the United States. At the end of the war, the US ended Lend-Lease and, simultaneously, Britain needed to move from a war economy to a peacetime economy. These upheavals led to a serious weakening in the British economy.
Perhaps the most lasting impact of this change was that it brought a Labour government into power immediately after the war. The Labour government started to create the British welfare state that exists to some extent to this day. In addition, it started the process of nationalizing many British industries. This transformed the British economy for decades.
In these ways, WWII had a tremendous impact on the British economy.