A fire door is a tested assembly
It performs as it was tested, with the hardware it was tested with. Every item either sits inside that evidence or breaks it.
What actually goes wrong?
Usually the hinges. A 54mm door with a vision panel and a kick plate is heavy, and hinges rated against a lighter test door will pass a showroom and fail a corridor.
Tech specs
Approved Document B and BS 8300-2 want opposite things.
One wants the door to shut itself against the latch and the seals. The other caps the force it takes to open.
So which one wins?
Neither. It is resolved by design, not by a bigger closer. Often an angle seal fitted into the frame rather than the door, so opening force drops and smoke performance holds. Cheaper at Stage 3 than on a snagging list.

Panic, or emergency exit
Panic hardware where the public is. Emergency exit hardware where users are trained and know the door. Decided by who is behind it, never by preference.
There is no such thing as a UKCA marked lever handle.
Hinges, closers, locks and panic hardware carry conformity marking. Lever handles do not. If a supplier says otherwise, ask what else they have misread.

What do we send back?
A hardware set for every door, each line carrying the standard it is classified against, so the evidence travels with the specification instead of sitting in a folder.
How a schedule is put togetherSend us the fire door schedule.