Thanks for your help.
I have to say, I post here and on other forums, and there is almost 0 agreement lol.
Some people tell me that because of misregistration not to knockout white text out of rich black using 4c rich black, but make a rich black out of 3c or 2c. Others say use 4c rich black, the printer should be able to handle it as long as the text isn't below 12pt.
It's a very confusing industry. Some talks as if the print presses can handle anything in any colour as long as it's not tiny, and others are telling me to make do with 2 or 3c blacks etc. etc.