Reading Lacors it states that a six storey converted premise into self contained flats should have fire resisting doors across the stairway between, fourth and fifth and first and second. The premise I've inspected has flats (FD30s) opening directly onto a stairway with an AOV (head of stair) and no lobby or FD30s across stairway. The property is a converted Georgian townhouse (converted 1996) Basement (2 flats), Ground (2 flats), 1st (1 flat), 2nd (1 flat), 3rd -4th.(2 flats per floor). There is a secondary MOE on the first floor with FD30s to the neighbouring premise. Travel distance is 40m from top floor to ground exit/30m to cross corridor secondary MOE to neighbouring property. Grade A LD2 in place. Obviously taking Lacors guidance would negate the AOV. Who's right? TIA.

LACORS only applies where a conversion isn't to post 1991 Building Regulations. A 1996 conversion & AOV suggests to ADB and stay put, however there are lots of other factors you mention which are not! 

The fire strategy from the conversion would help (unless lost) as it would explain the rationale. Smoke control is also to benefit the fire service as well as escape and it's likely it was introduced as such under Building Regs so you can't negate it as there is an absolute duty to maintain it.

Not straightforward and certainly not possible to be definitive on here.