In article , Stuart Noble
says...
Insurance companies ask whether you have 3 lever deadlocks fitted but
it's obvious that, in the case of thin doors, they're worse than useless.

If the OP is concerned about the risk of burglary, I'd be tempted to
replace the entire door and possibly the frame too with something more
substantial. It doesn't matter how good the lock is if all it takes to
gain entry is a firm kick at the door. The lock would just smash out of
the surrounding timber.
--
David in Normandy.
(The free MicroPlanet Gravity newsreader is great for eliminating
rubbish and cross-posts)