No one answered but I finally found a solution to my problem (at least on Office 2010):
Drag failed email from Outbox folder to Drafts folder on Outlook
Now you can double-click the message to edit the failed sending account
I just use the From pulldown to select the correct sending account
Now click Send and it should go OK
Now all I need is a rule to try the alternatives automatically or at least pop up a menu!
The Mac is much better because if sending fails it automatically pops up a window to allow an alternative account/server to be selected.