The only success I've ever had with locks is by drilling them out. Once I've drilled enough to get a screwdriver in, I then force the lock. You need to be very careful not to damage the surrounding panel.
Other options to try first might be checking every other key you can lay your hands on. Or getting a locksmith to open it then they can either make you a new key, or reconfigure the lock so it's keyed the same as one of your other locks.
NB, the only reason I've had to drill out locks is because a couple of spare parts car wrecks I've bought have had incomplete sets.
Thanks for the tips. Ill give the drill a shot not happy to use the grinder with potential sparks against the checker plate. As stated I have a new set of locks should have replaced them earlier.
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