hm, replaced freehub and seal and used the mavic "special" grease that came with the seal...
wish I knew what it actually is (or at least an appropriate grease) as buying packets of it isn't exactly cheap, thin white stuff
and although it's no longer draggy it still seems to be, erm, catchy?
Spinning the wheel up still results in some drive train movement, which I guess still indicates some friction in the contact between the freehub body and the seal or the hub shell, or in the gears, hm will probably have it apart again to see if I'm missing something extra stupid like the outboard gear dropping into the splines for the inboard one due to a spacing issue, or even just not pushing the seal in far enough.
Plus side of the extra freehub is I can now attempt to get the front plate off, get the knackered bearing out and pop round to the bearing shop near work knowing that at least I have a usable enough backup wheel when the Hunt pops yet another spoke...
Suppose I could possibly get 28mm tyres onto my MTB 12mmx142mm rear wheels if absolutely necessary, though both are a bit off true... ok more than a bit, plus side... Hope racket.