My mate when working darn sarf in that there london town, used to save a few quid by kipping on a matress in his van.
He was woken up one night by the sound of smashing glass, and saw an arm coming in through the window. Imagine the surprise of the scum bag when it was whacked with a metal bar!!!
I dont advise kipping in your lock up, but it might provide some comfort that there is one less scrote who will be willing to stick his arm into your premises.
chains, locks, chains and some locks and a few bear traps! Spike strips on the roof?
I take it you dont put any razor blades around your doors etc then?