Some things to consider:
1. Granger loves the navy and the sea, so I cannot see him deciding to be a stay-at-home earl. 😀
2. I don't think that being on the Privy Council will restrict his activities at all. This was a different era, and it is inconceivable that a gentleman and an aristocrat like George would be tortured for information, even by a more cutthroat leader like Napoleon.
3. If you think of the timeline here, we are almost up to the Peace of Amiens, which is what the next book will focus on. Right now it's a boring time, more or less, on the high seas, and a good time for Granger to put his home affairs in order.