is larger and more diverse (& tolerant & a far larger market
Take the CIA annual stats handbook and check your numbers. Commonwealth is around one third of the GDP of Eu. If recomputed in purchasing power or GDP per capita due to these being rather low for India and Pakistan it is even less.
So as a matter of fact, the commonwealth is smaller than Eu using any standard market assessment metrics known to man. Except the delusional Kipling recital ones.
It is also not a uniform market and there is no free (or even facilitated) movement of goods and services by any means. At all. There are tariffs, limitations and external agreements by countries (including with the Eu) which prevent them from giving any sort of economic significance to the Commonwealth as an entity. So as a matter of fact - it is not a market. It is a construct for the purposes of exercising nostalgia.