2.5m is 8 foot 2.4 inches according to Google (decimals in measurement that are in inches is a thing? I’m metric so don’t know).
The standard ceiling distance between floors must be 8 feet in the U.K..
The joists and surfaces between floors in a home are 12-14 inches thick in total, bringing the distance between the floor and ceiling in each level closer to 7 feet.
The joists go on top of the studs, not between them.
'standard' ceiling height is 2.4m.
I’ve phrased that badly. Obviously the stairs go floor to floor... wall height would obviously be floor to floor minus joists, flooring, ceiling material.