How to secure front UPVC door?

[user1489844432]

My 2yo is able now to open the door by himself and he tried to leave the house couple times. Our door is UPVC so cant put night latch as it looks like they dont exist for this type of door. We put thumbturn type of lock as apparently this is recommended in case of fire but this is also reason little one is able to get out. Any ideas what else we could do apart from changing to key lock?

Can you put a bolt at the top? A handyperson would be able to get hold of something. Other option if there isn't a letter box or cat flap there is you can hang the key somewhere higher and use it instead of the thumb turn.