Ha. So, this morning (early, I hasten to add), I settled down to start work, only to find that Visual Studio 2005 had very thoughtfully eaten TestDriven.Net. I had a lovely greyed out "test with" option against my test project.
Oh well. A quick re-install of TestDriven, and we were up and running (after a mis-click on UAC permissions panel due to tea deprivation killed the first install).
Lets hope that is today's major frustration out of the way - although I still have food shopping to do, and urgently need to find some duck pancakes..