The petrol shortage (Colin's answer) happened at the same time but was mainly the result of the oil crisis of autumn 1973 (the second arab-Israeli war, sometimes known as the 'Yom Kippur' war because it started on that Jewish holy day).
An interesting facet I remember is that areas were split into 'A' and 'B' districts: 'A' districts were only allowed electricity on Mondays Tuesdays and Wednesdays, and 'B' districts only on Thursdays Fridays and Saturdays. Naturally offices all wanted to be in A districts and shops all wanted to be in B districts but of course this couldn't be arranged.
Fortunately the winter of 1973-74 was very mild, so few people now remember the disruption. Also, computers were not so heavily used then as now; most offices ran on typewriters, pen, and paper!