Your Silver membership doesn't end until 31st October. I wouldn't worry too much about when your flights credit, it's when you took the flight that's important.

Just phone them up once they credit (claim if they don't) and then ask for you points to be credited to the previous year and membership updated.

My year also finished yesterday at 530 points and I'm due to fly on the 22nd of this month. Confirmed with Exec club that I can extend to this date as within two weeks of year end (just!) and they will update membership once they are credited to Silver.