We rented a car to drive all over Ireland some years ago. (Glad we did, the best way to see what you want)
its a total game-changer with google maps, or some sort of gps.
it gives you total directions, what lane to be in, what's coming up ahead of you, etc.
I think we would have gotten lost multiple times without it, as the street signs in many cities are very small (sometimes just on the side of a building)
If you're renting a vehicle in the uk, be sure to get (and get familiar with) some type of navigation (they will rent them with the vehicle)
If you've got good insurance (might even be included with your credit card, ours was) with gps and someone helping you navigate, you'll be fine!
You've got to get used to the narrower lanes for sure, but once you're used to that it's no problem!