Thanks, I took another look at it this morning and the error was in my Administration.config file I hadn't given the full provider class name - schoolboy error on my part but with a clear head this morning it's so much clearer.
Thanks for the links to the additional two blog posts - I had read Carlos' in the past but will re-read again, I hadn't seen yours but it covers some key and useful points which I will post a link to on my blog soon for the benefit of the delegates who attended my Usergroup talk on IIS last night.
Thanks! :-)