we wanted to replace our reliable but boring Toyota Argo with another small second car, an EV mini was a good option, though the range was a concern. I figured the balance of weight and range would be ok with the mini. I had expected the range fully charged to show at around 130 miles on the car display, but 106miles is the highest at 100% charge so far. I’m not sure if there will be 30 miles left when it goes down to 0% or maybe it will improve when the weather warms up. The cars performance is outstanding, it’s the nearest to a motorbike I have driven.
The GOM (guess 'o' meter) is the one thing I don't like about the SE. It is hideously inaccurate, so ignore it. I've had mine for over 2 months, and it still says 180km when I charge to 100%, even though I drove over 200km and charged at 20+%. It doesn't learn. The best thing to do is look at your bars. I get around 250km per full charge (ie 100-0%), or 200km for 100-20%. This translates to around 30km/segment of the battery meter. A quick glance will easily tell you your range (segments x 30km). In miles, that is around 18 miles per segment. Alternatively, you could say 150 city miles range = 1.5 miles/% of battery. Whatever you do, don't look at or listen to the GOM. Even when you reach 0%, you still have 10ish miles left.
I will say that I live in a hot climate, so my range may be different. The best thing to do is to drive normally, then when you charge, work out your efficiency (ie. miles/percent used). So if you travelled 80 miles, and recharged when the battery was at 35%, you can travel:
80/(1 - 0.35) = 80/0.65 = 123 miles. For example, my last top up was after 154km, and 38% left = 248km total range (till empty). Once you establish this figure (for me it is 250km) you can accurately work out your range and ignore the GOM. Hope this helps.