Thanks for these tips, given i couldn't really see much wrong from psychical inspection of the locking mechanism and I don't really know anything about anything I will give this a try before the inevitable spinning disc treatment that I feel is imminent.
Have you tried putting key in the lock and turning it to put tension in the mechanism then tap/bang the lock body?
I had a d lock that would seize up and I could get it opened by banging it on the stand or whatever I was locked to.
Maybe take a hammer and try hitting the end of lock body while turning the key?