Hi
Sorry we didn't see this. You have two options the ISitecoreContext provides a GetHomeItem method which uses the settings in the site node of the web.config. This is ok but will break in the page editor on multi-site solutions, this isn't a Glass bug but is to do with the way that Sitecore resolves sites.
A better alternative is to use an ancestor query using Sitecore XPath, you can do this via one of the query methods on the ISitecoreService or as a property on a model using the Sitecore Query mapper.
If it helps we can offer consultancy to show you how to achieve this. We also cover this topic on our training courses.
Thanks
Mike