It’s standard practice to give clients a hard drive of the shoot they paid for. Unless your contract had a weird clause about how only your agency has rights to it and how the clients waive their rights or something along those lines, you’re probably obligated to give it to the client. You’d need to talk to a lawyer though.
Either way, handing over the video may not be a hill you want to die on. Again, it’s standard for agencies to share files/assets with clients. Also, clients want agencies that make their lives easier and having to argue with the agency about getting the video footage they paid for could really damage the business relationship.
If you want to talk to them about your agency’s future with them or continuing to work on larger projects, I’m sure there’s a way to bring it up in a healthy way. But I don’t think this is the segue for that.
"Не подражайте другим. Найдите себя и оставайтесь собой, ведь «зависть — это невежество», а «подражание — самоубийство». Дейл Карнеги"