I'd advise that, since you're a stranger, it'd be best to be patient and most times let the other guy go first.

Remember in Ireland you're driving on the left, and in Germany and Italy you're driving on the right. This means that a Left hand turn involves a very different manoeuvre - in Ireland it doesn't involve crossing any carriageway, so the question doesn't really arise, but in Germany and Italy it does, since you drive on the right there.

Now if it was a Right return it'd be the other way round.

If there's a roundabout (which can be only a couple of feet across) you'd cross off-side to offside. If it's an unmarked crossroads, the UK Highway Code (which is available online) rather leaves you on your own to make the choice:

"When turning at a cross roads where an oncoming vehicle is also turning right, there is a choice of two methods -
1. Turn right side to right side keep the other vehicle on your right and turn behind it. This is generally the safest method as you have a clear view of any approaching traffic when completing your turn.
2. Left side to left side, turning in front of each other. This can block your view of oncoming vehicles, so take extra care."

Happy motoring...