Offside to offside in the UK and Ireland unless road markings indicate otherwise, or it's a wide intersection where everyone else is doing it the other way - in which case go with the flow. You will probably find roundabouts more of a novelty to start with, but they do work. It's fairly universal across Europe to give way before joining them, as intuition would suggest anyway - again unless road-markings indicate other priorities.

You'd be VERY inlucky to get hassle from the Garda in Ireland. Strip searches at the border? Liz should be so lucky. And I think you can ignore most of the generalisations you're likely to hear from Liz and others about national driving characteristics. There are good and bad drivers the world over. (But in Ireland keep in mind McGrath's point about use of the nearside lane, when you're lucky enough to be on roads that have them.)

Mudguard, I'm just back from Croatia, which included 300km of driving in Italy. There was no mention of those reflective vests. Hire companies neither provide them nor advise about them and we certainly didn't ever hear that they were required. Presumably, for the moment at least, any visitor would get a fool's pardon.

(McG, it took me for ever to work out what you were talking about with that reference to "turning on" a red light! I'll be all right when I've wken up.)