@tothinkofsomething "Is there statistics on this?"
Yes, there is [sic]. If you want a direct county by county breakdown of exam results to prove intelligence in specific subjects, Ofqual have done that for you, just here.
Here is a breakdown of the GCSE top scoring counties by subject, for those who just want the top line:
Maths - Buckinghamshire
English Language - Oxfordshire
Music - Cambridgeshire
Geography - West Berkshire and Oxfordshire
History - Rutland
Biology/Chemistry/Physics - all London
Art - Rutland
Economics - Devon and Oxfordshire
Religious Studies - Rutland and Hertfordshire
French - Buckinghamshire
London not looking too shiny there, is it! Good for scientists, but if you want a broad range of subjects other counties appear to be at least as good, if not better, if pure exam results is used to demonstrate intelligence.
Foreign languages were interesting - if you look at languages such as Arabic, Urdu, Chinese, Polish, it becomes clear that diversity isn't limited just to London. There are either a lot of people who speak these languages natively across the country, or a some really good teachers outside of the capital.
I've managed to bite my tongue and keep my thoughts on the OP and their intentions on starting this thread to myself, but top marks to some of the amusing replies here - they've brightened my morning! 
And @mumduty - yes, thank f you've moved back to London! Goodness knows the rest of the country doesn't want your sort hanging about with your superiority complex! You know someone who worked on Game of Thrones! Wowee! So do I! I know several. (I bet they aren't the same people though. I know horse wranglers and stunt people.) But what the fuck does knowing someone who worked on GoTs have to do with the price of fish?