Guys, thanks for all of the answers and info. This is a great help so far.
Agent47, thanks for all of the help regarding the TCA's. I'm going to take a serious look at those.
Etches & Hayesey, the diff would be tempting. However, I've got to source an ATV box first (running an 8P). Once I have the box (which will need a bit of extra saving), I'll start looking for diffs. Thanks for the offer, though!
Hayesey, thanks for the info regarding the brakes. The reason I'd like the suspension adjustable in situ is I know I'm not going to get the damping right first time and it will probably take a few drives to get it perfect. I've currently got the front shocks on 2 1/2 turns out of 5 and the rears on 2 turns out of 5. As it is, it is too hard. It skips across the road on poor roads and definitely needs to be softer. I'm sure once I soften it up, I'll likely want to try a bit harder or softer yet until I'm 100% happy with it.
I know the carriers are very important to the 256mm setup. Assuming I just got those, which calipers fit? I think I'm correct in saying that the list of suitable calipers is bigger than the list of carriers. Or am I talking nonsense?