Can someone explain to me really simply what the difference is between Native & TDM Plug-in’s? I’m looking at the waves plug-in’s and it’s saying add to cart Native or TDM… Is either one better than the other? Cheers 
There are a couple of things to consider here.
TDM is an actual PCI card that is installed in your computer with it’s own processor and memory that way it does not tax the computer.
Your computer is a “native system” which means your processor and ram goven how many plugins and tracks you can record and play back.
There is a lot of debate on this. I’ve included a link to a KVR discussion on the subject and also another one that I found on the Avid website.
Basically, you probably want to go with the Native versions unless you are working with high end equipment. The extra performance in TDM is minimal compared to the extra cost that is involved.
http://www.kvraudio.com/forum/archive/effects/2003-11/29528.php
http://duc.avid.com/showthread.php?t=83152
http://www.gearslutz.com/board/so-much-gear-so-little-time/107740-tdm-vs-native-questions.html
Nice one mate, much appreciated