Hit a deer while driving in Scotland - rental car company charged me £2,000

Driving through the Scottish Highlands at dusk, a deer jumped into the road. I swerved but still hit the deer and destroyed the front bumper and headlights. I was fine, and the deer ran off, but the car was NOT drivable.

The rental company towed it and billed me £2,000 for the total loss of vehicle use and repairs. I thought I was covered because I bought their "insurance" at the counter, but it turns out it didn't cover "wildlife collisions" (what?!).

My travel insurance had rental vehicle excess coverage, which reimbursed me for the amount the rental company charged. It took 2 months to process, but I got the money back.

How does liability work when you're driving abroad?