As you've discovered, the insurance is a huge premium to the price. We take a trip every year to either Ireland or Scotland have always used our credit card insurance coverage. If you have a card that includes rental car insurance in Ireland (check carefully), you can save a lot of money. Be sure to have proof of the coverage and check the right CDW box. Some people find the idea terrifying, and that's fine.
The premium for an automatic is more modest. Last May we rented a car in the Outer Hebrides and they didn't even offer manuals, which is closer to the reality of their cost of cars.
In 2016, I managed to find a half-open gate with the side of the car, putting a pretty severe scratch down both doors. When we checked the car back in, they rang up $4000 in damage (absurdly exaggerated) and charged my card that amount. When I got home, I called the card company (Citi) and they got right on it. It took almost a month for the negotiations between Enterprise and Citi Visa to complete (mainly because of the time difference), at which time the charge was taken off my bill and they even removed the extra driver charge we had signed up for, leaving me with a $178 total cost for a two week rental.