Netflix calls it Season 9, but IMDB calls it Season 8.
I just got done watching it. Foyle (and Sam) are still working for MI5. This surprises me a little. On one hand, it’s obvious that Foyle wants to serve his country wherever he is need; on the other, he seems too straightforward and open to survive for long in a place where spies work. He certainly knows that some things are being kept from him. (Side-note: this season sees him once again resigning due to circumstances; naturally, he is soon back.)
This season does an excellent job of capturing the post-war mood of Britain–shortages of goods; people wondering if it was all worth it; etc.
We see a different side of Hilda Pierce in the last episode, which ends on a bittersweet note.