@mr_cr9 i have good news today that can reassure you even more
we are going to travel on 17/7 a family trip my lil brother didn’t receive his first child british passport so this is what i did
wednesday 13/7 –> sent an upgrade email
friday 15/7 today (48hours before) –> received a call ,passport was then printed and collected from victoria
going to travel sunday 17/7
PS: i did go to my nearest HMPO today because i was in the 48hour mark
overall they did it in 2days so this success story proves that it is possible to get within 2 1/2 days i hope this eases your worry
lmk if you need anything else