>> But that still begs the question, is there a reason you suggested .Visible False?
Yes, you typically want to hide the form after a successful postback because a) this will help the user understand the form was submitted successfully, and b) it prevents them from (accidentally or deliberately) submit the form multiple times. If you need to keep the form visible just don't change it's Visible property as it's visible by default.
I presume I can simply add some <br /> elements to move the "Message Sent" Label down,
Yes, that would work, or you can put it in a <div> which causes it to flow to the next line automatically.