I can see where you are coming from zunera happened to me as well!
I had issues with passport (applied through JCAP) as passport office kept saying the passport can't be issued as they haven't received the confirmation of ceremony attendance.
After speaking to few people in HMPO and when they read out notes on the application it became clear that they certainly get a confirmation of approval usually a day or 2 days before the date mentioned on the letter. In my case date was 31.3 but HMPO had 29.3 as approval date.
It was reconfirmed when earlier this week I called for my wife's update and they said the application was approved on 12.5 but we only got the letter on 27.5 with 13.5 as approval date.
Key however is that you can speak to someone nice who is willing to provide updated notes
Keep faith I'm sure your letter will come soon or may be by the time you read this