My wife and I (from Maryland in USA) did a driving tour of the UK and Wales in August. We rented a Jeep at Gatwick Airport and yes, the steering wheel was on the right side of the car (towards the center of the road as you drive).
We drove about 800 miles over 10 days, but most of that mileage was in large chunks on a couple days, with some days having very little mileage.
We stayed in Bristol (England) one night, Cardiff (Wales) two nights, Aberystwyth (Wales) one night, Betws-y-Coed (Wales) three nights. At that point we started heading back towards Gatwick Airport, but before we went back there we returned to England and spent three nights in Eveshan/Honeybourne area in the UK.
We did cross the Severn River on the M48 bridge, which was cool.
Another highlight was partially hiking up Mount Snowdonia. The days we were there it was rainy and foggy, and so we did not go all the way to the summit.
I'm not going to try to list all the roads we drove on, but we were on M roads, A roads, and (I believe) B roads, and even narrower roads. As people who are not used to driving on the left side of the road, we were relatively comfortable on the M roads and the A roads. The smaller roads were a different story, being that many of them in places had either stone fences or vertical hedges right next to the road, and many of them had water drain grates on the side of the road which (1) we were not always able to avoid driving over and (2) were not always smooth.
We drove because especially in Wales, there are places we wanted to go which are not served by public transportation.
I believe my wife wants to return and do a similar trip for Scotland. I haven't yet gauged how she feels about doing more driving, though, so I can't say for sure.