I went down to the London passport office this morning having had no luck on the phone. The lady was from the upgrade team and actually quite sweet, she assured me that I would receive my passport before my flight next Thursday and to follow up on Saturday morning and she gave me her name to quote in the email too. Still seriously nervous about it but left feeling a bit better and less tense. I was also expecting the queue to be around the block for people with enquiries but there were maybe 10 people.