At the start of WWI Britain was known for its professional army. Did Britain's army ever recover from the immense losses it suffered during the war? At the outbreak of WWII was Britain's army a renowned professional fighting force again, or did they rely on volunteers and conscription?

The British Army at the start of the First World War could be called 'professional', in the sense that it wasn't conscript based but relied on volunteers, unlike the other major powers, and didn't introduce conscription until 1916. However this wasn't necessarily seen as a good thing as it translated into a smaller fighting force. Keep in mind this was before complex modern equipment that requires much training to be used effectively and the kind of numerically lopsided victories like we've seen in the Gulf wars didn't really happen. Otto von Bismarck quite nicely expressed these sentiments, asked what he would do if the British army landed on the German coast, he replied that he would have them arrested. By the time of the Second World War, the British leaned on conscription from the very beginning, a good thing, as they knew what to expect from a war between industrialised states. They also had an army command that was full of veterans of the previous war, who expected another position war won by attrition, thus being caught unaware by blitzkrieg. Based on this I would say that the British were in some ways better off in the Second World War than in the First, from a purely organisational point of view, though they were still prepared for the previous war rather than the present one. It is also important to remember that non military wounds of the War, social and economic, had yet to heal hampering the British.