Tom Sutton

If the flats have no fire alarm you could consider cam action doors closer which is extremely efficient, allowing the closer to be set to provide reliable closing power for fire door applications yet still be easy to open.

You only require to update if there has been a material alteration that has made the means of escape worse.

Why? but if you do need an alternative fire escape route, escape through the garage could be acceptable, but the two routes would have to be separated by a minimum 30 mins fire resistance.

There is a few libraries throughout the country that give free access to BSI online, but it must be viewed in the library premises. Most universities give free access to their students and you can take out BSI membership, at a cost, and get standards half price. Other than that it's an expensive game.

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In the 60/70s the only door I remember had cold smoke seals was, smoke stop across corridor doors, used to divide up long protected corridors, into 60 feet maximum length.

The regulations are concerned with the upholstery not the frame and although the frame may be pre 1950 the upholstery is not. If it was reupholstered in the late 80s early 90s then the who ever upholstered it is subject to the regulations and should have attached the appropriate labels to comply with the regulations. Consequently if it carries the appropriate labels no problem, if not, you could have problems if you try to sell it, and I think you would be outside the law.

It does appear that many schools fitted with fire sprinklers do extend them into toilets and there has been fires extinguished by them. However this would be up to the sprinkler design engineer to decide the layout and if they are required in toilets. https://shop.bsigroup.com/ProductDetail/?pid=000000000030337104

As far as I can see it depends on the temperature of the room, if you study the links above I am sure you will find the answer.

You do not require an escape window if you have a protected escape route (protected staircase enclosure) to outside the premises. As for the size I cannot help you there check with planning or building control.

I think it is sufficient to know that fire will spread upwards, sidewards and downwards, fastest upwards, slower sidewards, even slower downwards but will spread in all directions depending on the construction. If you want a more scientific approach then google "research on downwards spread of fire" I am sure someone will have researched it. For a new flats development, an architect would use ADB or BS 9991 or an engineered solution, I know ADB or BS 9991 requires 60 mins separation between every dwelling which I think would not be achieved by a double layer of plasterboard, but I would need to research that.

First of all what type of fire door are we discussing a FD30 or FD30s fire door. If it is a FD30 door then intumescent air transfer grill could be acceptable and to do what you suggest I would contact the manufacturer to obtain their advice.

It looks like the staircase is open to the dining room which would not be acceptable, again a proper drawing is required and I would not try to give any suggestions without it.

I cannot make sense of the drawing, you need a proper architects drawing with measurements and what is half hour fire resistant.

I cannot see why not the fire inspector will take the responsibility and I suspect he/she will be calling you back if you do not get it right.