That's not actually proof of anything other than Snowden is wanted for something and the PM is worried that the press have classified information. It's not actual hard proof of what the NSA and co have been up to.
Like I said, I'm not saying all these revelations are lies, but as an intelligent & reasoning being, I require proof before I'm convinced.
The documents of some (all?) of these leaks are public AFAIK. I haven't looked to much into it, but I've seen the one where they explain how they use that tracking software of theirs. This being espionage with extremely damaging consequences for regular people and politics alike, it would be hard to find secondary sources. There would have to be additional whistle-blowers (unlikely due to the effect this would have on one's life and the lockdown Snowden triggered), spy agencies coming clean about the whole thing (won't hold my breath for that one) or "official investigations" (which would end up 99% redacted to the public).
To summarise, you have to read the leaked files that are public and make up your mind about them and/or trust (or not) the journalistic integrity of the people publishing these leaks.