Cheers pollyp, that's very clear. Didn't realise I'd need new looms as like I said I was hoping that mine provisioned for ABS (lots of unused plugs around!). Doesn't really seem worth it now (although master cylinder, hubs, calipers and brake lines aren't at all a problem.. fairly easy.)
When you say cabin loom do you mean the entire wiring loom needs to come out? (i.e. dash + carpet + trim out job?).
Since you're clued up on rear brakes, could you tell me whether any other Nissan uses the same (or compatible) rear calipers as I can find a couple of rear disc beams, but they need new calipers, and the only Micra rear calipers I can find cost a BOMB.