viewing HTTP posted message content

Hi everyone,
please can someone help me here. I thought this would be a walk in the park, but oh no! Perhaps I'm missing something simple...like my brain?
I am trying simply to read a value posted using XMLHTTP to a psuedo ASP.NET 'web service'. It is clear how to get all of the HttpResponse properties(formally serverVariables) out, but no way can I get the actual posted XML message string out to start working with it....

I simply want to grab the posted xml string in my sub Page_Load and carry on from there, with the intention of creating a total webservice solution when time allows.
Am I going about this in totally the wrong manner?

I will not attach code as nothing has come even close yet except 'Request.InputStream', with which I hit a dead end.

Any suggestions greatly appreciated...

Thanks

Neil