I walk dogs on the right, and I think I’m right in saying that that is the most common way. Certainly I do tend to end up with the dogs in the middle when passing another.
Actually, being right-handed, I’m not sure how comfortable I’d be with the dog on my left.
I’m in Scotland, but it’ll be the same in England.
I’m right handed, American and was taught that the dog belongs on the left (although training him on both sides isn’t a bad idea, in case I lose an arm someday or something - but that’s each side on different walks. On no account should he be weaving and switching sides during our walk!) I like it because while I hold the leash with both hands (the loop in my right and the mid-slack with my left, to keep a good control while we’re learning to heel), my right side and hand are still more free to do things my right hand is better at, like open doors and hold coffee cups and push a stroller.
If the dog is under your control, having him walk in the middle when someone passes you shouldn’t be a problem because he won’t be tugging anyway. If it is a problem, it’s time for an obedience class refresher.
This extrapolation has cropped up here before, and it’s not the case. There are indeed differences between countries as to how pedestrians interact, but there’s not a direct correlation to driving, nor do all countries have a ‘side’ you can easily identify.
Why is it disturbing? The way people interact obviously varies between cultures and between countries. In some cases there’s a strong tendency to walk to one side. In others, people manage to pass on either side, with a mutual understanding of body language making it work - in the case of Britain, it’s the eyes looking to the ground on one side or the other before moving there.