Well, I have somehow got it working.
I reset the router to factory defaults, connected and rebooted the STB & PC in the prescribed order. When the PC rebooted I noticed that the Prevx Pro and ZA Pro icons in the systray had both enabled without any hold up. So I opened IE and blow me down, straight to Google without Ntl registration or using the D-Link setup site.
Thanks Chris, not sure how it cleared, could it be DNS delay ?