Since we are using GDAL (1.8.x) for raster data input, this page might help you to setup the required XML description file for describing the corresponding WMS server: http://www.gdal.org/frmt_wms.html
If you need more support you could also post some more infos about the WMS you want to access and we can try to figure out, which paramaters to set in the required GDAL-XML file...
Since the call to:
does not return a XML specification of this service, I don't know how to get to the required elements for the GDAL XML file.
This sample request demonstrates an expected and usable XML server reply:
Maybe you can check for the bbox of the service in LL84 and also figure out the ground pixel resolution of the highest resolution layer?