like i said, it takes longer to showup on the tracking system, becuase they can get 1,000s of letter a day, and it takes time to go thru their system because of the quantites (well thats what the guy at the P/O to me)
you have something called Section 3C protection. That is, as long as the application is made before the expiry of the old visa, that old visa will be "treated as continuing" until the application for a new visa is decided, even though its stated expiry date has passed.
The Section 3C protection will continue until the visa application is agreed and the new visa issued, or even if the application is rejected, until the time for appealing against that rejection has expired. And as long as an appeal is made, the Section 3C protection will then continue until the appeal hearing, etc..