I think you want the dative "tyrannis" rather than nominative "tyrannus".
https://en.wikipedia.org/wiki/Latin_declension#Second_declen...
https://en.wikipedia.org/wiki/Latin_declension#Second_declen...
https://en.wikipedia.org/wiki/Sic_semper_tyrannis
Legitimately asking. I'm not sure why it would be anything other than "Thus always to tyrants".
"Rest in peace" is well known, but "Rest in pieces" is neither unhead of, nor wrong. It's a riff on a well known phrase.
Same here: "Thus always (do) tyrants"
As I said, I think it makes more sense here. I think he wanted to call the UK government tyrants, not the spied-upon people.
(Maybe the poster will weigh in and save us the trouble of deciphering his intent :)