Mark, could you update your details to show the correct car? Your profile is reading "not an MG" although you say in the post that you have an SE LR.
The worst I've ever seen from the GOM on my SR is 145 miles at 100% charge, and that was after a series of three-mile journeys in freezing conditions with a lot of pre-heating and the heater on at max while driving. I think that went down to about 132 miles when the heater was switched on in the car.
I tend to think that the 100% range for the SR and the 80% range for the LR are fairly similar, so maybe you're not far out for the winter range, as
@tsedge says? I gather that the LR battery can take as much as a couple of hours to balance if it hasn't been balanced for a while, so I would let the car sit at 100% on an AC charger for as long as it wants. You can tell it's balancing because the app shows the finish time as the current time and the car is still drawing power (may show as 0.0 Kw but it's still doing it). When the app no longer shows anything for finish time or charging power, it says "not charging" at the top, but you have a figure displayed for "remaining range", then it's done.
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