OK The F8F's look lovely, and the offset should be pretty well spot on. BUT, at 7" they are going to be very wide for even the widest - 205 - tyre you're going to be able to get in the rear arches. I guess they'd just about be OK with 225's, in which case you could take a gamble and commit to a bit of rear arch surgery a la Simon Owen. I'm speaking from memory here, but I would have thought you would be able to weld and redrill the hubs for that pcd.
A bolt on spline hub sounds promising, but don't forget that the spline hub will sit outboard of the normal hub, so you will need the already unusually large offset of the P6 hub plus the depth of the spline hub to give you an unfeasibly large total offset. Or you could use gebuine Rover splined hubs - but they are like rocking horse poo.
Chris