Have a look at the postcode here : http://status.o2.co.uk/
If it's B1 then there is ongoing work...
Your service might come and go until we've finished.
Updated 12:30 (refreshed hourly). Recent faults might not show yet.
I think optimisation is needed.
I think EE would be needed more by me if I had as many problems as you do with O2.
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