I find winters in the southern UK desperately dull and depressing. We seem to be stuck under constant gloomy skies and damp from mid November to mid February most years.
Would much prefer something a bit colder and brighter in the winter, with more chance of snow. Not extreme Siberian conditions, but just more seasonal and less SAD-inducing.
UK summers are of course not great either, but a good deal better than winter. At least the sun shines about half the days, it's light until at least 8pm, and you don't get pervading damp that hangs around for days after it's rained. Spring, and early autumn (September, early October if we're lucky) are the seasons we do best. In winter I'd prefer to be somewhere else in all honesty; if I could escape the UK for three months each winter, I would do. Either a Mediterraean climate (mild bit bright) or a more classically wintry climate (brighter, and more frosty with occasional snow) would do. (As it happens I am currently out of the country, but not for as long as I would like to...)