For a snowy Christmas, flying from Britain to Germany only makes sense for the Bavarian Alps, and even then just 5 of 45 resorts. Only Zugspitze is flawless: at mid-mountain, 1,800 m, natural snow lay over the holidays in all 30 winters 1984/85–2013/14, and no other resort in the country has that record. Behind it come Grasgehren and Garmisch-Classic on 27 of 30 each, Oberstdorf with Nebelhorn on 25 of 30. Half of German resorts manage 17 holidays out of 30 or fewer.
Mid-altitude mountains don't work without snow cannons
Even in the Alps, Sudelfeld at 1,200 m manages just 18 snowy Christmases out of 30. In the Black Forest, Feldberg gets 2, in the Sauerland Winterberg gets 5: there the holidays depend on snowmaking, and with it 32 of 45 resorts clear the threshold of 25 out of 30. For comparison, Austria has 62 of 134 resorts that are snow-sure, Switzerland 63 of 95. The numbers describe climate, not a forecast (methodology). The conclusion: at Christmas from Britain you're better off in Austria or Switzerland; Germany is fine for a short trip and for Zugspitze.