I think a major reason for the indifference is ignorance. Many people here in the UK are not well informed on this issue. I'm shocked at how many people I've spoken to about this and they're only hearing it for the first time. Apart from the Guardian no major news outlet that I have seen has given this scandal any prominence. They have mostly acquiesced with the recommendation from our security services that they don't report on this issue. In my opinion another scandal in itself.
Another factor may be that people in this country don't think the risk of tyranny returning as credible. They don't believe that the danger posed by mass surveillance will ever be anything but hypothetical, that somehow a free society is our national destiny. This shocking complacency manages to both totally ignore human nature and the lesson from almost every history book ever written.
As a country I really hope we get real about these issues and that we stop taking our hard won civil liberties for granted. Ultimately they're the only things that can be trusted to truly protect our democracy.