I have no doubt that the EU would eventually try to force Britain and Ireland (which they're trying to get them to call the “Atlantic Archipelago“ instead of the “British Isles”) to drive on the right side of the road like the rest of the continent; they’ll probably push it by pointing out
how Sweden converted from left side to right side in 1967,
and against the will of the people, coincidentally the same year they introduced speed limits in Sweden. The railroads, not so much—after all, they let France run their trains left-handed, like in Britain and Ireland and even on the former Chicago & Northwestern today.
Salve
Not wreally friend. If you will call English person European or Irish person as well, you will have different conversation, if you will call me I am Russian, or Polish person Ukraine, you will found yourself in serious unconstructive debate.
Reason English metric system is in use, is because of trade agreements that must be fulfilled, though if you go to these country, if you are native, you use metric system totally. Either you like, you have metric system on your products as well, there is reason for that.
Merci.