Jonahbird's post in VoxATC UK was marked as the answer
Having stirred a little hornet's nest here, I feel I should add what I hope is clarification.
I purchased version 5 of VoxATC UK & Vox ATC X plus 4 x 16 bit voices in August 2008 from RC Simulations. I have just found the DVD :rolleyes:. It contains: VoxATC X; VoxATC UK; 16 bit UK voices and 16 bit US voices.
In December 2010 I purchased the update to Version 6 from VoxATC. Along the way I also purchased 4 Cepstral voices.
It seems that when I recently upgraded my PC I should have installed the DVD first, and then upgraded by downloading the latest version - 6.49, and using the appropriate registration codes.