Yes it looks like the problem is national,everyone reports having no data and some members say they've no network at all.
I've never seen the giffgaff Twitter feed so busy at this time in the morning and of course there's nobody on duty to answer questions til 8am so there'll be some really peed off punters by then I would imagine:_
This is a Global issue caused by an outrage at Ericsson of Sweden.
It is out of O2 engineers ability to fix.
So unfortunately all we can do is to show patience until it is fixed.
There are over 45 million subscribers in the same boat.