I had the same problem, and found it quite frustrating. You could try logging out of your account first by signing out via Settings -> iTunes & App Stores, closing the app store manually (double tap home button, hold app down and 'minus' it) and turning off & on the phone again.
Unfortunately for me, this didn't work - and after spending a while at it, I got fed up, backed up my phone via iTunes and restored. This fixed the issue. However in hindsight, something I forgot about was to 'soft reset' the phone. I would give this a try - just hold the sleep and home button until the phone switches off and release, it will then restart.
I couldn't figure out exactly how it happened in the first place, but I think it was because I tapped a link to an app via Safari that wasn't available in the UK app store, and it went a bit mad.
Hope this helps.