Yes, you're absolutely right. Strictly speaking the use of the present
perfect here with a specific time reference in the past is wrong.
It can be explained (though still not grammatically justified) by the fact
that this is an announcement of a „new“ event which still feels very much in
the present (even though everyone listening already knows what has happened), so
the present perfect feels appropriate.
But don't forget that this is also a set-piece historic
announcement that will go down in the annals (the written records) of British
constitutional history, and that's why the speaker feels justified in adding
the date of the event, even though that would usually require the
simple past.
So in the socio-historic context, a form of words has had to be found which
reflects the „news“ (present perfect) but also tells us when it
happened (for the official records) and it's a (grammatically
incorrect) compromise. All in all, it doesn't grate on the ear here, and they
won't send the speaker to the Tower of London to have his head chopped off.
On the word order point, you're right that SVOMPT is the standard word order
in a normal declarative statement. But this isn't a normal
declarative statement, it's a news announcement, an announcement about
something that has just happened,. so in terms of
its rhetorical (= emotional) impact, the „when“ (time) element is more
important than the „where“ (place) element. So the „time“ information is
brought forward to give it greater prominence. The „place“ information
(„at Balmoral Castle“) is of secondary incidental importance, so
it's relegated to the end of the sentence.
- Hey, have you heard the news? The Queen has died!
The natural rhetorical (emotional) response here is:
- Oh really? When (not where) did that happen?