Correct I meant fire lining, when I was searching on internet I came across some paint they sell that can be used to convert normal solid doors to equivalent of FD30 fire doors, I wish I had known about this as I had already purchased my door by then, and indeed you will need larger door stops, every council or building control may differ in exact requirements, so it might be best to check with them, but personally a living room and lounge is not a sleeping place so I would not have thought that you would need a fire door there, kitchens only need a fire door if you were renting an HMO, not if you donme a loft conversion and a dormer.
Check this site for fire resistant and intumescent paint paint :
https://www.rawlinspaints.com/home/...-upgrade-kits/1168-fire-door-paint-30min.html
As for fitting Fire Doors, it is recommended to have an even all around gap of 3mm, to allow a fur lined intumescent strip, the fur helps prevent smoke penetrating through apparently, if assuming the door is still cool and further away from the source of fire, so the intumescent material would not have expanded yet.
I said apparently, because, whilst the intumescent material tucked inside a grove cut into the frame or alternatively into the door edges, as initially the smoke needs to be prevented from escaping from the gaps, whilst the intumescent strip is still cool, so the fur lining stops that, and when the heat reaches the intumescent strip, only then it would start to expand and seal the gap more strongly.
But in an experiment, I found a small flaw with this method even though it has not been covered anywhere, initially the heat would first react with what is outside the grove, that means the fur (made of nylon) would heat up and melt into a molten state and run down into a blob, leaving a wide open gap, and then there may be some time like 60 to 90 odd seconds before the intumescent strip had enough time for heat to reach and react with it ( it is well tucked in the door frame or door edge, and wood is a poor conductor of heat, the strip requires about 200C before it reacts!
So it would start expanding, In my experiment i carried out, by taking two pieces of timber, screwed together forming a 3mm gap between the two and rebated a channel 4mm deep to take the intumescent strip, the furred edge of the strip covered the gap, so when I heated the gap with a hot air gun, this is what happened, the furs melted, then for some time the smoke would just pour out of this gap, for a minute or two, (which caused me some concern) before the int. strip reacted and expanded to seal the gap.