Take it to a dealer and get them to change the lock barrel.
Mine packed up on holiday a couple months ago and wouldn't unlock, then after a bit of fiddling the whole barrel of the lock came out on the key. I went to the Motorrad dealer in Challons, France on a busy saturday morning and they couldn't have been more helpful.
It was one of those jobs where you're in someone else's hands and have to wait as long as it takes and pay whatever they want. They put some other work to one side to sort me out while I waited, and the salesman made me a coffee and offered a go on their new GSA Demonstrator.
30 minutes and £30 later I was on my way again a lot happier.