By Matthias Williams and Kate Abnett LONDON/BRUSSELS (Reuters) -Record-high winter temperatures swept across parts of Europe over the new year, bringing calls from activists for faster action against climate change while offering short-term respite to governments struggling with high gas prices. Hundreds of sites have seen temperature records smashed in the past days, from Switzerland to Poland to Hungary, which registered its warmest Christmas Eve in Budapest and saw temperatures climb to 18.9 degrees Celsius (66.02°F) on Jan. 1. In France, where the night of Dec. 30-31 was the warmest since …