Update to our case, for those following timeframes etc.
01/14 - Package sent to Carol Stream, IL
01/16 - Delivered
01/22 - Text Message received (G-1145)
01/23 - Check cashed
01/24 - USCIS Case Tracker confirmed status changed to Biometrics Scheduled (For 02/11)
01/27 - Chat with agent via EMMA and received my online access code - Biometrics Notice, Receipt and Green Card Extension all held in my online account
01/31 - Receipt and Biometrics Documents received in Post
02/01 - Green Card Extension Document received in Post
Service Center is the National Benefits Center (NBC).
Now the long wait begins, but glad to have received everything so quickly, as due to travel in a couple of months, so no worrying about receipt of original extension letter or missing the biometrics appointment.