The impacts of La Nina on Europe are not as strong or as straightforward as the impacts on North America, and there has been considerable scientific debate on this topic. Some studies suggested that northern Europe tends to be warmer than average from mid to late winter during La Nina, and vice versa for El Nino, but there also have been studies suggesting that the impacts of ENSO over Europe are sensitive to details like the strength of the event, the sea surface temperature anomalies in the Atlantic, and more. A key factor for Europe may be whether or not we see a sudden stratospheric warming, as friend of the Blog Dr. Amy Butler wrote about several years ago. Therefore, I recommend keeping eyes on both the tropical Pacific and the air high above in the stratosphere if you're trying to predict impacts over Europe.