EV Database has the Countryman ranges as below. It’s worth noting their winter is -10 degrees and their mild has no air con on at 23 degrees outside. From that and with your mileage I’d be expecting 200-230 winter and 270-300 summer unless you’re doing short trips along country roads driving like you stole it.
Real Range Estimation between 170 – 350 mi
City – Cold Weather * 230 mi
Highway – Cold Weather * 170 mi
Combined – Cold Weather * 200 mi
City – Mild Weather * 350 mi
Highway – Mild Weather * 215 mi
Combined – Mild Weather * 270 mi
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Mark