This might be "teaching grandmother to suck eggs", but I thought it might be useful to someone.
Fitted a new cat-back exhaust yesterday (standard mild steel), and here's what I've learnt.
It can be done by jacking up the NSR (and using a stand and chocks).
Cut the old rubbers off (make sure the new ones are the right type first!)
NSR handbrake cable gets in the way, but can just be unclipped (2 places) rather than removed.
Use exhaust assembly compound otherwise it'll leak
Loosly assemble exhaust (don't tighten clamps) and move into position. Old bits of formica covered chipboard make moving the exhaust around on the ground an awful lot easier (and quieter).
For me, a vegetable box/crate thing was the right height to support the first silencer, and an A4 paper box on end supported the rear box at the right height. Whilst not exactly perfect, it's a lot better than trying to take the entire weight of the exhaust yourself, or straining the front pipe.
Attach the middle outer rubber first, fit exhaust together, then fit middle inner rubber (attach to body first, otherwise it's impossible).
Remove rear mount from body (single 13mm bolt). Fit to exhaust and reattach to body. Sillicone spray helps to fit mounts. Needed to be removed as prongs were too long to fit rubber in-situ.