Thanks Renato,
After a lot of playing around, I more or less came to the same conclusion as you, although I ran the script at the command line specifying the proxy. I'm not sure whether specifying the proxy actually made any difference as I didn't test it without beforehand.
>groovy -Dhttp.proxyHost=proxy.host -Dhttp.proxyPort=8080 C:\Docs\geb.script.groovy
This then pulled all the dependencies down into the grapes folder. I'm still having issues, but more with the specific functionality, so that's one for another thread!
Thanks for the reply
CK