OK, so I followed steps to extract the Packs.zip file and ran the System Update Readiness Tool (SURT) again [which on my machine took about 30 mins to complete]. I had little faith that this was going to do anything, I had spent weeks, months most likely, looking into this problem! This process of running SFCFix and then zipping up the CBS folder and sending it in is probably going to prove a big waist of time.
Yet low and behold, I went to my Programs and Features window, clicked "Turn windows features on or off" and the box is now populated!!!! This absolutely worked to solved the issue for me.
Question, now that it has worked for me, should I or could someone change the subject of my Thread. Currently it is "[Win7SP1 x64] SURT total detected corruption count: 399." But unless someone reads further in, those looking for how to solve the "Turn windows features on or off" box being blank, may miss that this process worked for me and my system.
Cheers all for this great forum!!