Battleground events are probably the best for NW England, providing the cold air wins out. 5th February 1996 is the more recent standout example, but in the past I believe late January 1940 was a monster event. The circumstances of the war meant that not much information about the event was made public.
Arctic winds swinging round from the northwest are good for Irish Sea streamers (December 2009 & 2010), but even better are when polar lows and troughs develop in the flow. December 1981 is probably a good example (I wasn't around then though). I think 28th December 2000 was a polar low event.