IPhone :: Cannot Download Apps, Music Or Books From The ITunes Store?

Since I updated to 5.1 on my iPhone 3Gs, I keep getting problems with the updated OS. I can't download apps, music or books from the iTunes store, it's very hit and miss. It is pointless having a pin upon wake up of the phone as all you have to do to get past the pin is by swiping the camera button up to by-pass it. The battery life has dramatically dropped from lasting a couple of days with everyday use to around 9 hours. The signal from the network has dropped from 3 bars on 3G to 4 bars on GPRS, and finally apps keep crashing and exit themselves to the home screen.

I have rang my network (O2UK) and they have said that they have had serveral reports of Apple products having these bugs since the release of 5.1, and saying that nothing has changed in terms of te settings and masts near me, but they advised me to check my network settings and if they are different from what O2's website said (they were the same). So why are there so many bugs with 5.1? I can't download any apps at all and my battery is worse?

Info:
iPhone 3GS, iOS 5.1, Bugs with iOS 5.1 and iPhone 3Gs