Is it ok to use an iPad (or similar consumer hardware) and electronic charts for GA in Europe?
No, these kind of apps (AirNav, VFRNAV etc.) are not meant to replace paper charts. You'll find phrases like this on most of the websites which offer those apps you will find paragraphs like this:


  Please note that this software is not intended to replace a certified navigation device. You should always use official aeronautical documentation when preparing and performing a flight. You should always use certified navigation devices when performing a flight. [Source: https://itunes.apple.com/us/app/air-navigation-pro/id301046057?mt=8 ]


There is certified software like for example Jeppesen Mobile TC available.