N-E-E-ECROOOOO.
I just upgraded from O2 to Three because I was fed up of paying more a month (£21.99) for only 500mb of internet versus £18 a month for a 1 month rolling contract with loads more mins, texts and their 'One Plan' data which includes unlimited data & tethering.
Did a speed test at home to compare the speeds and went from 3.67down/1.61up with an 88ms ping to 12.01/2.23 with 48ms.
Now if only the battery on my Nexus 4 would last long enough to make it through the day...
Good choice, I moved from Vodafone to 3 because they were shitbags who douched me around.
I've been with 3 for about 4 years now (originally on a 30 day rolling, now on a proper contract because it meant I got a Galaxy S3 and unlimited texts and internet and basically unlimited minutes (2000, lol)) and I'm very happy witht them and their service.