It probably won't help much, as we lodged in London. However we've not had any acknowledgement, other than the confirmation from the courier to say it was delivered back in March.
From my digging around on the web, it seems some people have received acknowledgement in the past, and other's haven't. At one point I did ring the number on the immigration website and some poor bugger (it goes through to Oz, and it must have been about 3am over there) went off to look in their system. They said all the 461 documentation gets uploaded into the system (which begs the question, why the hell do we have to send paper docs in the first place?!) and that he couldn't see that it had been uploaded yet...
But as Paulhand says the world has been in lock down, so while it's annoying I'm not surprised.