ok with a bit more tinkering I got this working - you should go to desktop/system settings/sound card detection.
This should see the logitech device, and do the standard sound test and you should hear it.
you will then need to in your skype application change the input to use this device /dev/dsp1/
You will then need to go to your standard volume controller and under "file" select "Change device" and yourn headset should be identifying itself. The input is almost definitely muted by default, so you need to turn that on.
Trust that helps!