The 6800Ultra will maintain a high premium as stocks dwindle. It's the fastest PS3.0 card available for an AGP setup, and there are still lots of people who are happy with their current AGP systems but want a gfx boost for new games. The 6800 is their only option without upgrading mobo too, so the demand for AGP is still there.
I'd expect OcUK's price to go up again, when stock is down to 5 or 6 cards.
As for the PCI-E version @ $999.99, that's just insane!