One old passport sent to Corby
Still not updated as received although it has been signed for.
One same day One old passport sent to Peterborough they have updated as received a few days after.
2 applications and old passports sent to Liverpool they have updated as documents received 2 days after signed for delivery.
So all depends on the offices and as long as you have tracked your delivery and have a signature it’s most probably reached the offices but needs to be scanned in or assigned to an employee.