Help! My lock's seized up and my bike is trapped!

I very much doubt that a lock you recently used is now 'siezed' it could've been a bit stiff which wouldve totally been solved by the GT85. I think its likely to be some sort of mechanical jam.

Id recommend a lot of jiggling about/shaking it/hitting it.

Also bear in mind that someone may have glued your lock which is surprisingly common.

I dunno if you remember or even if I told you but this happened to me. Then I snapped the key off in the lock trying to force the key. Cue me not being able to work and having to wait 4 hours for someone to come with an angle grinder