The company have been working to rectify the problem all day, which is believed to have been caused by a software glitch in equipment supplied by Swedish company Ericsson.
CEO of O2, Mark Evans, tweeted this afternoon:
The company said one of their third party suppliers had identified a software issue in their system. Work is currently ongoing to fix the fault and customers are being encouraged to use wi-fi where possible. Companies that share O2’s network – such as GiffGaff, Sky Mobile and Tesco Mobile – are also being hit by the problems.
Last info said that network will be restored on Friday morning.