Thanks for the reply lano.
Thats pretty much what I've done then I think.
The only (and main) difference is I want to do this regularly so really want to do it all in mdadm or through command line rather than physically unplugging drives. Otherwise I will need to keep opening cases etc and my computers aren't that accessible.
It looks like I'm getting there, I just need a bit more confidence in exactly what everything is doing. Its one think playing with vmware, quite another with real data!