Setting default value from rules variable

Hi there

Sorry if this has been answered elsewhere but I couldn't find quite what I'm looking for.

I'm trying to use this module to set the default value of a text field in a webform. In my rule configuration, an earlier action creates and sets a variable and I want to use the value of this variable to populate the default value of the webform field.

I initially conducted a quick test using this module to set the default value of the webform field just using a static value and that worked fine. But I don't appear to be able to use the data selector to select the variable that was set earlier. I seem to have a limited set of options in data selector.

Have I missed something or am I trying to do something not supported by this module?

cheers
Kat