I know that Solihull emails are usually received earlier than Birmingham - they've been between 10pm and 1am previously.
Birmingham emails can take until late afternoon on 1 March to arrive. I understand they are sent in batches...Bham LA will have around 6 times more pupils to email than Solihull LA. But you can often log in online and see your child's allocation from there, from the morning.
A few years ago, my daughter's admissions page was not updated and I did not receive the email until the afternoon of 1 March, but because girls from Solihull with scores a little lower than hers had been offered CHG, we knew then for certain that was what she would get.
That's why sharing your info on here - especially if your child was a borderline score - can help a lot of other parents