I'm including an Iframe (The Google Chatback Widget) which uses an Iframe to display, is there anyway to alter the appearance of the content within the Iframe via CSS? I want to hide portions of the iFrame and make other parts bigger etc.. As it's hosted by Google I don't have access to edit the Iframe HTML directly.
No there isn't. CSS only applies to the page it is in and an iframe is a separate page.
You would probably find thaqt trying to manipulate the appearance of the Google supplied info is against their terms of service and so wouldn't be allowed even if it were possible.