I live in small purpose built (60’s) block of flats - 2 gf + 2 x 1st floor. Entrance lobby/porch with two flat doors off, then single stairway to 1st floor with two flat doors off small landing.  
Height of 1st floor flats under 11m. Have read guides but confused whether all flats or only some, or none, need fire doors. G/f flats also have garden doors and one upper flat has balcony for escape purposes. Cannot see specifically where it says fire doors are definitely required! Currently, no fire doors.

You (well the block freeholder or commoners) are legally required to have a fire risk assessment which will address this. Fire doors will be required to the front doors of flats opening into the single internal shared stair, however if these are the original flat fire doors and ironmongery and in good working order they will not need replacement  - usually the main fault with these is no self closer or one that doesn't work fully (usually as it's a single chain closer) and this can be replaced with a modern EN1154 closer to overcome this.
If a door has been changed from the original fire door and is no longer a fire door then this would need replacement. 

Internal doors within flats are not covered by the legislation affecting the block.

For your block only one guide applies & that is here- https://www.gov.uk/government/publications/making-your-small-block-of-flats-safe-from-fire

Thank you Anthony for that valuable information and referral to the guide. I would presume that fire doors are definitely required for the 2 gf flats despite their not opening direct to the stairs? They open to the gf lobby area with the stairs off that. Many thanks, again. The four flat owners are the freeholders and we manage the block ourselves

13 hours ago, Guest Mr Chris said:

Thank you Anthony for that valuable information and referral to the guide. I would presume that fire doors are definitely required for the 2 gf flats despite their not opening direct to the stairs? They open to the gf lobby area with the stairs off that. Many thanks, again. The four flat owners are the freeholders and we manage the block ourselves

Possibly, but without seeing it for myself I can't be definitive.