Yeah as you’ve discovered the range is really a guess based on driving style among other things.
Turn off the aircon is the biggest way to boost range, turn aircon off, set fan to 3 and set temp to Lo that’s the most efficient way to use it and keep the car fresh and not misted up.
It’s pretty steep hills around Scarborough which probably explains some of the high usage. Worth checking tyre pressure too as those dropping can add more drag, when I got mine the tyres were below the ones stamped on the car