It is a complicated debate.
There are various factors at play here - as suggested in a couple of threads, it is not just about how far north you are, but also how far west - Cornwall, Northern Ireland and the far west of Scotland will see the dawn 15-20 minutes after those on the Greenwich meridian.
In London the midwinter sun rises at 8.06, where I live in Scotland's central belt it rises at 8.46, and at Thurso, mainland Scotland's most northerly town, it rises at 9.06. Combine that with a dark and wet morning, and it is barely light till much later, but that effect is more marked as you move north - I don't fully understand the complicated calculations which relate to the density of the clouds and the angle the sun strikes them at!
One under-discussed point in this debate is why we are this year putting the clocks back 53 days before the winter solstice, and will put them forward again 94 days after the solstice - why not equal time each side of the shortest day? Would there be a reasonable case for a much shorter period on GMT - say, mid-November to mid-February?