The current Mini Cooper (F66 petrol and J01 electric) has a 12V accessory socket as standard in the UK, with USB-A and USB-C common on newer trims. If you add a two-port charger, check how it splits power, since two-port chargers almost always share one wattage budget instead of giving both ports full rated power.
Three products we would look at first in this category. Fit for your Mini still comes first: check the compatibility list on the listing against your exact model and year, and read the model guide above.