Don't want to depress you any further GillyHen but there's no happy medium when it comes to plot security. If they want to be in, they'll get in no matter what.
As others have said, if it means anything to you don't leave it at the lotty. The old fella behind me doesn't have a shed and consequently whilst we are all being broken into his plot is left alone because there's nothing to nick.
Does your site have lockable gates? If so, who is responsible for locking them?
We recently installed gates onto ours and (touch wood) have only been broken into once since they went on in November ish whereas normally we would have had at least 3 by now
![ohmy :ohmy:](https://chat.allotment-garden.org/Smileys/green/ohmy.gif)
If you can't take your stuff home with you, is there a secure association building that you could lock your tools into at night? It's a long-shot because most societies don't have anything that would fit that bill so really it is down to the plotholder to make sure thier valuables aren't at the lotty.
As someone said, make sure you report each individual thing to the police. You file your report, your neighbour separately files his and so on. It's not one break in, its lots of little ones so they have to be reported so that the police can a) be on the lookout for who did it b) add it to the crime statistics c) provide a better police presence around the allotments.
Police forces won't spend money on sending officers to an area where no crime is being commited so please please report it! (if you haven't already
![blush :blush:](https://chat.allotment-garden.org/Smileys/green/blush.gif)
)
EDIT: one thought though; how close is your plot to houses? Perhaps if you can rig something that makes a lot of noise it might alert people - after all, who does their gardening in the middle of the night?