I purchased some graphite lock lubricant from Maplins. It's in a little bottle that has a nozzle you insert into the lock and push in; the pushing action releases the lubricant by spraying into the lock. If you do get any I advise that you do this well away from anything you want clean. I rather stupidly did it with the key slot of the lock facing down and ended up with the graphite lubricant running down the bike and onto my stuff. It doesn't half stain.
I purchased some graphite lock lubricant from Maplins. It's in a little bottle that has a nozzle you insert into the lock and push in; the pushing action releases the lubricant by spraying into the lock. If you do get any I advise that you do this well away from anything you want clean. I rather stupidly did it with the key slot of the lock facing down and ended up with the graphite lubricant running down the bike and onto my stuff. It doesn't half stain.