MWIS do have a tendency to overdo the wind speeds.
But don't forget the predictions are for the summits. The felltop assessor on Helvellyn today measured an average 24.1mph gusting to 47.7 with a temperature of 1.8C. This was at 12.25. MWIS predicted 40-50 gusting 80 in the morning, but moderating to 30-40 in the afternoon, with temperature 1 rising to 3.
So about 10mph out on wind speed, and spot on for temperature.