I had an issue about 1:40pm with o2, both 3G and an o2 wifi hotspot; couldnt get anything to load beyond 15% for about 10 minutes; the 15% was almost immediate, then it just hung there and did nothing, I tried multiple pages, Google etc, all the same.
Not sure how long the problem had been going on for, as it was the first time I had tried to use mobile data all day.