Hackbridge doesn't appear to have any gates, nor do either of the Windsor & Eton stations. That's not to say there won't occasionally be someone checking tickets at the exit from the platform.

You can take a virtual tour round any station in the country at http://www.nationalrail.co.uk/stations_destinations/ - type in the station name, then from the station page, click the Stations Made Easy 'show [station] route' link. Click on the map to expand it, and you'll then be able to mouse over the plan to see pictures of the most mundane details.