I've not seen in the press this year any suggestions that we should keep the clocks set an hour early all year. In previous years there have been some (south-eastern) opinions expressed that Scottish and northern opposition to the idea should be ignored as "a few dairy farmers in Shetland might have to get up in the dark for milking"
A spot of Googling yesterday (as though I don't have enough to do at the moment) found some figures for sunrise, sunset and day length for December 20th. In brief, the further north you go the shorter the day is, and the further west the later the daylight begins. Penzance is the most southerly town or city on the mainland, Thurso the most northerly. Lowestoft is the most easterly, Kilchoan the most westerly.
(In order of sunrise time. Format is - place, co-ordinates, sunrise, sunset, day length)
Lowestoft, 52°29' N 01° 46 E, 08.00, 15.44, 7hr 44min.
London, 51°30′ N 00°07′ W, 08.03, 15.43, 7hr 49min
Brighton/Hove, 50°49' N 00°07' W, 08.00 15:56, 7hr 56min
Birmingham, 52°29' N 01°52' W, 08.16 16.55, 7hr 39min
Penzance, 50°07' N 05°33' W, 08.18, 16.21, 8hr 03min
York, 53°57' N 01°05' W, 08.21 14,43, 7hr 23min
Liverpool, 53°25' N 03°00' W, 08.25 15.24, 7hr 29min
Newcastle, 54°58' N 01°36' W, 08.29 15.39, 7hr 10min
Edinburgh, 55°57' N 03°11' W, 08.41, 15.40, 6hr 59min
Glasgow, 55°50' N 04°15' W, 08.45 15.44, 6hr 58min
Aberdeen, 57°09' N 02°09' W, 08.46 15.26, 6hr 40min
Inverness, 57°28′ N 04°14′ W, 08.57 15.32, 6hr 35min
Kilchoan, 56°41' N 06°07' W, 08.50, 15.44, 6hr 54min
Thurso, 58°35' N 03°31' W, 09.03, 15.21, 6hr 18min
These places are on the mainland. The Northern and Western Isles are:-
Stornaway Isle of Lewis, 58°12′N 06°23′W, 09.11, 15.35, 06hr 24min
Lerwick Shetland, 60°9' N 01°09' W, 09.08, 14.57, 05hr 49min
(Times are from here and co-ordinates from various places, so may vary in accuracy.)
Add into this the lower potential radiation as you travel north, due to the curvature of the earth. The sun's rays strike at a lower angle, and have to penetrate further through the atmosphere. It is estimated here that in winter while Penzance receives about 8 megajoules of solar radiation per sq metre per day, Newcastle receives about 5 MJ and Shetland about 2MJ.
Plus, cloud cover is affected by geographical position, so the Scottish Highlands receive about half the sunshine that Essex is blessed with.
So if you suffer from SAD, the further south you are, the happier you will be – and the lighter it will be when you have to get out of bed in the morning.