Thanks Steve.
Before I went away for holiday I put a huge (and expensive) lock on my welder, and put the keys somewhere that no one would think of looking - as it turns out, not even me.
I angle grindered the chain off, but the lock cost me about $150 so I would like to get it open so I can get the tumbler bit out so keys can be made up.
It's tough getting older and stupider and making f***ups like this