It does vary a lot. In city it's easily 4mi/kWh or more. But I remember being pissed at Stellantis when in cold rain on highway the efficiency dropped to 1.7mi/kWh, and the range estimate was still calculated based on the marketing number, going down by 2 miles for every 1 mile driven (it was a version without a heat pump).

Ioniq's worst case is better than this (~2.1 in bad weather, 3.1-3.3 at highway speeds in good conditions), and it displays accurate range based on real usage. Ioniq is indeed a bit too fat for UK's parking spaces.

on.to was great. I think they took advantage of tax breaks when leasing for a business, and during lockdowns they couldn't buy new cars fast enough.