Thanks Tony
Correct - the ground floor hall, first-floor landing and second floor landing have not been altered in any way (except decorating). Just the ground floor rooms extended.
I did make the point to him that we have not made the position regard fire safety worse. And he did...
Does anyone know if this is the case for a loft conversion done in the 1980s? Just had an extension on the back of my house, open plan with two (existing) doors leading to hallway. BCO is saying I need to replace every bedroom door with a firedoor to make the loft conversion compliant with fire...