Well, in the summer of 1940, it represents - outside the Raj - quite possibly the largest British professional ground force with a complete TOE.
What was evacuated from France was...let's see, 368,000 or so troops. A sizable figure, though of course they left virtually all their equipment in France and Belgium. Reforming and reequipping them into a major amphibious invasion force was going to take time, especially given the paucity of landing craft.
Dominion troops were a tricky thing. Churchill was able to gain quite a few to fight in North Africa. But without an active war in Libya, it's less clear where they go. The Australians were always reluctant to have their troops moved outside of the SW Pacific; and once the threat of invasion of Britain has passed, where do they go? Curtin's preferred answer would be a) at home, or b) Malaya.
In a strange way, it's a difficult situation for the British, if Italy stays neutral. The Mediterranean lifeline remains open, but they don't have the strength to invade France, or indeed anywhere else in German-occupied Europe. There's no war in Africa. I suspect you would see more resources diverted to securing the Atlantic, and building up air and naval forces - and a bigger force structure in Malaya.