On the VIN the last 6 digits are like the serial number, the digit before that on an Astra K should be either an 8 (Ellesmere Port) or a G (Gliwice), and the character before that is the model year (at the moment on all Astra K it should be a G, for 2016 model year), so a UK built car would have a VIN something like WOLBF6EAXG8******, a Polish one would be WOLBF6EAXGG******
Next year's models will have H as the model year.