'Ello Alex.

Lets see:
I get the impression DirectX is still live and well, and that this is a framework to allow .Net development upon DirectX. DO I have the right idea here?
From what I understand, XNA is a user-friendly wrapper around native DirectX, designed to make making games easy and fast without sacrificing any low level power.

If both SDK's still exist, what#s the main advantage/are the main advantages of choosing one over the other please - why would you code using the XNA framework as opposed to the DirectX SDK?
Taking into account my bias (I haven't used the DX SDK for anything serious, but I've been learning the XNA framework), I'd say the major advantages are as follows:

1) XNA can produce for the Xbox 360. You'd need to be an expert on DX and Xbox to do this with the DXSDK, if it's even possible.
2) XNA is easier to use.
3) XNA comes with a huge number of samples, starter kits, tutorials, etc. and has a good sized online community in which people who work on the framework frequently participate.
4) XNA is continually being updated, and often polls the community for what features should be implemented next.

Since I don't know what's going to be in XNA 3.0 (which should be out soon), I can't really enumerate on the disadvantages... most of them will be solved by then.

And again, I haven't used DX.

Finally 2 posts I read, albeit older ones (which prompted me to post here) mention this is only for C# developers??!?!! Is this true and if so, how on Earth is that possible as it would be a .Net framework IL option which surely would therefore be available to all .Net languages, no?
Wikipedia: "Games that run on the framework can technically be written in any .NET-compliant language, but only C# and XNA Game Studio Express IDE and all versions of Visual Studio 2005 are officially supported."

Since I'm using Express, I'm limited to C#. And it seems like the entire community (including tutorials and samples) writes in C#. And I know the above line doesn't apply when 3.0 comes out, 'cause it'll only have support for VS2008. But I imagine the trend will continue: buy Visual Studio and you can program with XNA in whatever language you like.