Thanks all for all your help! Relieved to say the passport arrived today, timeline below
Delivered by UPS ~8:35am on 1st September (Wednesday after BH weekend)
TNT tracking showed it was scanned & out for delivery 7:01am on 1st September (Wednesday after BH weekend)
TNT acknowledged they had it for delivery ETA 1st September shortly thereafter (Wednesday after BH weekend)
Passport printed and sent 10:50am on 31 August 2021 (Tuesday immediately after BH Monday)
Application approved 12:00pm on 27 August 2021 (Friday before BH weekend)
Messaged HMPO via Twitter DM 10:41 on 27 August 2021 (Friday before BH weekend)
Documents received 12:13pm on 11 August 2021 (Wednesday)
Posted old passport ~12:45pm on 9 August 2021 (Monday)
Application received 12:05pm on 8 August 2021 (Sunday)
Application submitted 12:05pm on 8 August 2021 (Sunday)
So around 24 days end-to-end … I’ve submitted the timings into the website so it should contribute to the accuracy of the algorithm …
GOOD LUCK GUYS!!! 🙂