Problems with Coldfusion Web Services

Hi,

I am trying to get a web service to run through Coldfusion for the first time and I'm having some problems (to say the least).

The web service I am connecting to requires an XML string as an argument which must take the form of

<?xml version="1.0"?>
<Request RequestType="AvailableToSell">
  <Data Product="1169_7" MtrxCode1="F" MtrxCode2="135" MtrxCode3="" MtrxCode4=""/>
</Request>

Code (markup):

I have tried building this as just a string and then passing that to the web service e.g.

<cfsavecontent variable="blah">
	<?xml version="1.0"?> 
	<Request RequestType="AvailableToSell">
		<Data Product="1169_7" MtrxCode1="F" MtrxCode2="135" MtrxCode3="" MtrxCode4=""/>
	</Request>
</cfsavecontent>

<cfinvoke webservice="http://test.co.uk/wsdl?targetURI=urn:omlink" method="wsomhandler" argumentscollection="#blah#" returnvariable="sResult">

Code (markup):

But this returns an error

Web service operation "wsomhandler" with parameters {ARGUMENTSCOLLECTION={ <?xml version="1.0"?> <Request RequestType="AvailableToSell">  <Data Product="1169_7" MtrxCode1="F" MtrxCode2="135" MtrxCode3="" MtrxCode4=""/>  </Request> },} could not be found.

Code (markup):

I've also tried several other ways using cfinvokeargument etc but still no luck. Can anybody out there help? I'm running out of ideas as to what I'm doing wrong.

Thanks