Mild spoilers ahead:
Not as clever or bombastic as the other two movies, but it's a great movie. The tie ins with history were well done (to me at least--the usage of important characters and events were within the realm of possibilities), and the misleading of who is the main protagonist is very well done. I spent most of the movie preparing for the dad's death, and was not prepared for the alternative.
This movie was entertaining, interesting, and had a good variety of set pieces, and a decent enough motive that has its grounds in a real life (believable) conflict. I don't live in England not Scotland so I can't attest to if this is a common stance, but I can suspend my disbelief enough to enjoy the movie.
5/5, can't wait for the next Kingsman. It's my favorite movie series, and it's never disappointed.