Fixed. The Windows clipboard is no longer cleared on opening an Office 2010 Application.
With the "third party" comments as the stimulus, a logical troubleshooting process quite quickly revealed the Microsoft SharedView plug-in to be the cause. Now disabled by opening Word, navigating to File\Options\Add-ins\Manage COM Add-ins, pressing [Go], un-ticking the SharedView plug-in, and saving the change.
My employer has recently stopped using SharedView in favour of the (excellent in my experience) Microsoft Lync unified communication platform (which has a Word plug-in that works!) so disabling the SharedView plug-in matters-not. In fact, I might as well get rid of SharedView!
Thanks for the "third party product" pointer that set my train of thought.