> In the UK where I am, most standard (not budget) property policies would cover theft from an unlocked entry point.

How is this supposed to be assessed? You can demonstrate that a door was locked, if some kind of obvious measure was taken to circumvent it (destroying the lock, destroying the door, destroying the window...), but you can't demonstrate that it was unlocked. Burglars aren't limited to destroying things to bypass locks. One obvious approach is to pick them.