Confused regarding door latches

20 Oct 2020
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United Kingdom
I've purchased some new interior doors which are DX30 style and look as follows:


I have also purchase door knobs on a rose.

I am now trying to work out what type of latches I need.

The lock stile is 110mm in width so it is my understanding I need something like a 75mm backset latch so that the knob has enough distance from the frame to stop your hand hitting the frame when you open the door. Does this sound correct?

The knobs themselves are unsprung. Is my understand correct that I need "heavy duty" latches which contain springs ?

Additionally, I'm unsure as to if I need a tubular or mortice latch. If I understand correctly, the tubular latch is easier to fit and requires less removal of wood from the lock stile which no doubt the fitter will thank me for.

However, my confusion is compounded when it comes to the bathroom door which will have a door knob and a lock (dead bolt?).

I've seen mortice locks that contain both the part of the main handle and the lock in one fitting. Should I opt for this or a separate tubular latch and dead bolt?

I'm pretty certain in my previous house the strike plate on the bathroom door was one piece of metal. If I buy a latch + dead bolt there will would be two strike plates I presune?

Not sure if that matters or not - would welcome some general advice.

Many thanks.
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