Sorry for your troubles, but this is one of the most entertaining threads I've read in awhile! Quite a freak show full of grinning idiots.
If the fat lady bought a walk-up fare on a transAtlantic flight, CO certainly charged enough to give you some compensation. Your first deal to shift from BizFirst to Coach is irrelevent here; even on a free ticket you were entitled to a full seat.
At first I thought you were going to resort to sitting in a crew jump seat, but the available crew rest area (normal) seat was such an obvious alternative, it does seem like they were giving you a hard time.
I guess if you're really desperate there's always the toilets or the galleys - maybe that would get the crew's attention!!