I was attempting to create a grid with borders, using the same test app as my last post . I thought it wasn't going to work, then I found a webpage that linked to an MSDN article How to: Create User-Resizable Applications with GridSplitter .
For some reason that guy didn't think the MSDN articles worked. I've not been through all of the code I gained my answer without doing so. Maybe he's right, maybe he's not.
The solution I found was to create the separate grid row/column for the borders, the linked pages do talk about the GridSplitter, I was going to test using that rather than a border. Since the pages suggest the use of a separate row/column I figure that the GridSplitter works in the same way. I guess the way the WPF layout system works prevents the collapse behavior that web developer would be familiar with from using a HTML table ( see here if interested).
For now I think that might be enough practice with the grid control. I don't really need to be able to do this right now, but I have learnt a few bits from doing this testing.