Some thoughts based on my experiences driving in England:
Consider maybe getting train passes instead?
OK, I’m not entirely joking. Using trains, public transportation, and taxis (Uber?) can end up saving you a lot of stress involved with driving (driving on the other side, directions, traffic, parking). That being said, Britrail passes are not cheap.
My biggest issue with the switch to the other side was judging my position. Other people have noted their position in the lane while driving, but my biggest problem was parking lots…er…car parks. I had the damndest time, when pulling into a space, figuring out how close I was to the cars next to me.
Absolutely get a GPS. We’re used to big, green street signs with white letters in the US. In the UK, you get a tiny white sign on a lichen covered wall off to the side of the road, and ivy is growing over it. That’s if there is a street sign. Looking up turns on Google street view ahead of time is a great idea too.
Highways aren’t designated North, South, East, West. They’re based on destination. For example, if you’re going from Heathrow to Stonehenge, you’ll take the motorway (freeway) to A303 toward Exeter (not A303 westbound). Coming back, you’ll take A303 toward London (not A303 eastbound).
In the roundabout, I typically stayed in the left lane to make an easy exit, but this bit me in the rear end a few times, when I ended up in an “exit only” lane and had to exit the roundabout earlier than I wanted to. Be cautious of this.
There are no yield signs. The white dashed line painted on the road (such as in front of a roundabout) means to yield. You’ll find this to be very important.
Be conservative in your driving. Better to piss people off because you’re being overly cautious than to piss them off because you’re running into them.