Ok, So after months of trying, I finally got it working. As I thought it was an install problem because after installing correctly I didn't have to fiddle with any settings in Sonar, it worked immediately.
So here's the steps I took.
1. I cleaned up any previous files eg steam folders and vst's from existing installs.
2. Re-installed each DVD from original package, I installed the vst to program files\cakewalk\vst pluggins.
3. Installed Omnisphere Patch Library Update v 1.5.5
4. Installed Omnisphere Software Update v 1.5.5e
5. Installed Omnisphere Soundsource Library Update v 1.0.2
6. Installed Omnisphere Software Update v 1.5.6d
7. Run vst scan in Sonar..
Works Perfectly!
Before I followed everything above but once I added step 6 and installed the previous version of the software update over the top of the other one, everything worked beautiful!
Very happy with my Omnisphere now!
Thanks for all your help. Hope this helps someone else in the future.
Josh