Can you advise on how readily applicable the CMMI is to a conventional manufacturing environment, I understand from the book and other SEI publications that the model is infinitely tailorable but when you get down to the SP level it is very software centric.
Well, that would have something to do with it being written by the "Software" Engineering Institute!
The CMMI is a process model for product development, and the Goals are the required components. The PRactices are expected, and DO often read like a software product model, but they can be replaced with alternatives of your choosing - as long as those alternatives add up to achieving the Goals in each Process Area.
So yes, the CMMI could be used, and often is, in a manufacturing environment. It's a great set of guidelines for product and project management.