Ryan, thanks so much for taking the time to answer, and so comprehensively too, I really appreciate it.
My client came around after I suggested that Getting quality backlinks to a website full of coding errors was like hanging a crystal chandelier in a toilet!! and that they where tying one of my hands behind my back by not sorting it out. Perhaps not the most expert answer but they got the point.
Thanks for some great information and a great answer all round.