Well, gone back to the brew after a week, and it's plummeted to 1012, 4 points lower than predicted. This suggests it weighs in at >7%.
The down side is that most of the sugar has turned to alcohol, so I am left with quite a bitter, dark beer. The spice seems to have disappeared under the hops. However, I seem to recall that all my brews were hoppy on being kegged, and the softened in the barrel. I hope so, because this will be difficult to drink at that strength and bitterness!
Biggest problem of all, is that I still have mild left in the keg....that's tonight's mission sorted, then!