Issues in plane travel can happen for a number of reasons, but very rarely do they happen because of anything going wrong with computers.
As Wikipedia notes, winter is not the best season for traveling. The people from the UK who were out for a trip during the Christmas holidays which are close now must have regretted their particular choice of day and time.
However, it was not the faulty weather that had hundreds of customers stuck in the Heathrow, Gatwick, and Stansted airports. A server problem made all the activity stop on December 12, 2014. The incoming flights had to be received, but the airport soon became full because no flights were taking off. Some landings had to be directed to another airport than initially planned one.
That must have been a stressful day for the passengers who had transfers, as well as for those who had to sit for hours. The National Air Traffic Control Services (NATS) confirmed that the system was fully restored the next day. To calm down all the people caring about data, they denied the possibility of a hacker attack.
The flying agencies and the customers will most likely start craving payment for the discomfort that they experienced because of the delayed trips. A disruption of this scale will lead to some huge expenses, but the facility has been through technical issues before and that did not hinder the further activity.