There are two obvious areas of difference between the Brits and French. One is language, though both languages have the same Indo-European Celtic heritage and have been influenced by the same kind of social changes. The basic difference is that the English have stoically hung on to their Anglo-Saxon roots (old western Germanic: Dutch, German and Danish). French on the other hand is a Gallo-Romance language based on Vulgar Latin with a strong Dutch influence giving them all those sensuous round vowel sounds.
As for the other reason – Why do the Brits drive on the left hand side of the road? Historically it’s to keep the right hand free to fend off attackers and stop their scabbard hitting people on the road. According to historical references, the French drive on the right so they can sit on the left hand horse pulling the wagon and whip the rest of the horses in the team.