Google breaking its contracts over Analytics Premium would severely negatively affect it, given that it's a product a number of very large companies and organisations use.
The NSA will just install their funnel somewhere new and off you go.
Browsing privacy is not just about the intentions of the two parties talking to each other but everyone one holding the wire plus everyone the other sites invites to listen in on your private exchange.
I don't think the NSA snooping on Google Analytics should really be in your threat model when looking at a UK government site. They could just ask GCHQ.