This is because French is/was the defacto choice for foreign language option in secondary schools throughout the UK, at least up until the 2000s. French was aft

This is because French is/was the defacto choice for foreign language option in secondary schools throughout the UK, at least up until the 2000s. French was after all the language of diplomacy and quite a bit more useful in European business last century than Spanish was. Spanish is now catching up and will likely over take in the next couple of years. Latest number of GCSE exam entrants were about 125K for French, 115K for Spanish and 35K for German.