Re: fitting bolts to an u&o door, you can even fit them on the outside. They aren't as well protected then but multiple padlocks reduces the ease at which any criminal can get in........
I was thinking "electric door opener" as then you can get rid of the handle, but the problem is if someone tries to crowbar the door open then you have got even more expensive damage to repair.
....... try less harmful deterrents too, there are automatic cat and dog deterrents that are connected to a hosepipe and shoot water when they detect movement. Permanently install such a system above the door and soak them. Perhaps you could even put a permanent dye in there somehow, tell the police to look out for a luminous purple scumbag.
It's a shame the break-ins are relatively infrequent, otherwise you could hire in a local paintballing team and offer cash prizes for direct hits to the knackers
But whatever you do, don't give them any excuse to sue you. Getting them wet will tick them off, but I don't think anyone has ever successfully been sued or charged with hosepipe offences (oo-err!).