Unscrew Seatbelt Buckle: How To?

I'm starting to despair because I can't get the seat belt buckles off my current seats to attach them to the new ones. The seat belt buckle is screwed to the seat frame with an M8 Torx screw. I have the corresponding bit, but my small ratchet just spins, and the large torque wrench caused an adapter to break. Even a cordless screwdriver or a regular screwdriver is completely overwhelmed. How the heck do I get this screw off? The official designation in the AKTE is: self-locking set screw M8*24.5. How does it lock itself? By the way, it's a SEAT Leon, so similar to the 1J Golf or A3, etc.

Hi,
With a proper tool, like a quality brand such as Hazet, and using an 8mm star socket directly on a 1/2" drive, it should be possible.