I've had the same thing through LeasePlan. Was meant to be week 39, got pushed to week 40, then 41, at which point I asked if they actually had a clue or were just fobbing me off.
Long story short they spoke to the dealer and they said it could be end of Jan now. Which I think is ******** as well and they're just saying that to keep me on the hook.
I'm honestly not expecting it to turn up before March. But I think they know that if they were honest with me then I'd cancel. But if they can keep me until Jan, then by that point I may as well keep waiting.