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?
Initially I could not solve it by your example in the first place. Getting errors all the time.
So I started to research and explore the GDAL WMS from scratch by my self. And that's always the best thing you should do by the way.
I've started with to get an image from a Web Map Service url. That's where I figured out the image scaling.
Then I tried to create a World File to associate with. Ended successfully.
And by going that way and using below description of the GDAL WMS I finally figured out how I should built the GDAL XML.
What also helped me to solve this, is that I could use InfraWorks beta debug screen to detect the errors.
Looking back to your example, your explanation is correct, but misses to my opinion some important details.
Scaling the image is the most important one.
I'll write about it in a blog soon.