offset spindle lever pad

Hi im wanting to change my door locking mechanism so that it cant be opened from outside without a key. I’ve checked my current lock and it only has a single spindle so i guess this needs to be changed. My fathers door once shut required the key to be fully turned to open but still operated...

I have recently moved house and the front door is a upvc type with handles having an offset spindle, lever pad type mechanism. This works as designed and the 'night-latch' facility works as intended. A key can be put into the lock from the inside or the outside. My question is:- can the...