We had a "pact" where the navigator could remind the driver at anytime to stay left/go left without getting pissed off. Generally the suggestion was followed by a thankyou. It worked well for us.
We had the same pact on our recent England/Wales/Ireland trip and it worked well for us also.
I know you said you were renting an automatic
@donyell34 ; the only thing I would suggest on that front is that if know how to drive standard (and like it), I think it's actually easier driving that than an automatic over there because driving the standard naturally keeps you more actively engaged and focused on driving. I was apprehensive because it had been almost 30 years since I drove on the other side of the road, but I absolutely loved it, and driving standard was a big reason why. But I really love driving a manual transmission; this is clearly not the time to learn if you don't.
As for the other side of the road thing, just remember that whether you're driving here or there, the steering wheel (i.e., the side on which you are sitting as the driver) is always the side of the car that is closest to the middle of the road. Believe it or not, just repeating that in my head when necessary made it pretty easy (I actually had to remind myself a few times the first few days we were back in states).
We did a lot of very narrow roads in Wales and Ireland, especially the Ring of Kerry and a few other places that were really out in the sticks. There will likely be times when you have to graze a bush or some other type of foliage on your passenger side (and sometimes the roads were so narrow that both sides of the car were scraping up against branches, etc.). For that reason I highly recommend paying the additional fee to bring the liability waiver down to zero, meaning that you will not be responsible for any damage to the car. I paid the additional fee for both of our rentals on our recent trip, and in both instances I would definitely have been dinged for damage that scratched the paint if I had not paid the fee, meaning I could have--and like would have--been charged up to the full deductible of $2,000. IIRC the fee was approximately $30 additional for each rental day.
I agree with the comments about the rotaries, not necessarily because they are so difficult, but because there are so many of them. Most of the time you are continuing straight through them, but we found it helpful for the navigator (i.e., my wife) to physically point to the exit I needed to take. Just stay to the left and put your left blinker on to let the people entering behind you know that you are getting off.
Don't sweat it. You'll be fine.