True but it is not the cold that is unusual, it is the duration of the cold. Normally at this time of year any cold snaps and accompanying snow last a couple of days at most before temperatures rise back into double figures. Currently we have had about three weeks solid of sustained cold with no respite and nothing to suggest any change in the near future.
Coupled with significant snow in places that hardly ever receive much in the depths of winter, never mind March (e.g. Channel Islands, Isle of Man) and widespread ice days (sub-zero daytime maxes) right up until nearly the end of the month, it has been a pretty exceptional March.