One time in my life I had shops that were always been broken into so I must admit to being a little bit keen on prevention, I would make the door open outwards so that it can’t be forced inwards, at the moment your door has very little torsional rigidity and so this would really help. It will also give you a little bit more room inside the workshop. I would fit jam bolts in case they attacked the hinges. Easy to do you need Coach screws with a half inch shank screwed into the edge of the door then you cut the heads off and when you close the door it marks the frame where to drill the hole – at a slight angle to accept the bolt, 3 should do it. Sheathing the outside of the door with zinc plate really puts them off, held in place with coach bolts right through the door.
This bit is just for information, the lock you have should be ok I think. I used to buy locks in Spain, I don’t know the name of them but it was the only place I could find them, they had a half inch square bar that slid about an inch and a half when the key was turned. They may not have been insurance security rated but they were incredibly tough, and I have never ever known a burglar to pick a lock.
In my present workshop if they do actually manage to get in, all my handtools are in a rack which I then put into my tool cupboard (with all of the above on that door as well). They don’t like to spend too long inside once they have broken in in case they are trapped so I think I’m relatively safe.Ian