Originally Posted by
btonkid12345
Yes, let's put this one to rest right here: there is no way DL is putting OP in business class, on DL or VS or any other airline.
When they make such changes, they have to "justify" to the computer/waive the difference in price that they are waiving to give you that seat. It will be thousands of dollars and no reservation agent or supervisor is willing to risk their job to make such a change for anyone - especially in this case.
OP - either accept a downgrade, a reroute, or a refund. Those are your options. A free upgrade to business class is not an option that is even remotely plausible (I wouldn't expect them to do that for me either, and I'm "Diamond" with DL so they should be able to be more "flexible")
Alitalia has done this

...but now, back to reality (agree, DL would never do this unilaterally)
Couldn't the OP Reroute SFO-LHR and then take the Virgin Train in First Class to Manchester and vice versa? or fly Virgin LHR-MAN?