Hi,
I will soon be improving a loft space accessed through a knee wall door (although not sure if I should be calling it a
knee wall as its 2m tall).

The door is currently about 850mm tall but I wondered about making it much taller to make access easier.

Currently the door has been made out of 18mm wood (not sure what).

The door is into the attic landing with 2 bedrooms off it. These both have proper fire doors and there is a further fire door separating the stair room from the main landing. The stair room has a sash window which I assume has been designated the means of escape from the attic rooms.

Therefore my question is what rules apply to my 'knee' wall access door? Should this have always been designated a fire door to preserve the escape route or are there different regulations for access to non habitable spaces?
And do any different rules apply if I was to make it taller ether for fire escape or anything else?