Hi,
No problem.
Well, again this is not really a SoapUI thing, as SoapUI will dispatch any request XML content you want.
In terms of namespaces, I can see that some of your elements already have namespaces defined e.g.
<MessageHeader xmlns="http://xxxxxxxx">
If you mean how to you define a namespace prefix, then you can do things like:
<h:table xmlns:h="http://www.w3.org/TR/html4/">
<h:tr>
<h:td>Apples</h:td>
<h:td>Bananas</h:td>
</h:tr>
</h:table>
(Example taken from http://www.w3schools.com/xml/xml_namespaces.asp)
So basically, you are already using namespaces and namespaces of any standard type can be used in the REST request body as you seem to have done already. Does that make sense and is what you were asking?
Cheers,
Rupert