AnthonyB

Both BB100 & Building Regs are for designing new builds and not always fully applicable to existing builds. Earlier schools will have followed the many editions over the years of BB7 and the risk assessment guide for existing schools is here https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/14887/fsra-educational-premises.pdf

There are loads out there: https://fire-surveys.com/ https://pyramid-online.net/index.php?d=1&d=1&refr=128 http://fireriskassessmentapp.co.uk/home/fra

Try these for advice - they are specialists in the field of making items like yours safe for general use https://www.flameprotectuk.com/

Building Regulations only apply to new builds, the DCLG guides replicate the approach used to good effect for over half a century and so as not to penalise existing buildings. The current approach offers enhanced safety, but the old approach still provides a reasonable level of safety in most situations.

Heats are a no no for escape routes as by the time they activate the area wouldn't support life. If you need a common system, the common parts have to have smokes. As a very small block by the sounds of it you may be able to retain the existing kit, without looking I can't be sure.

The premises should have call points first before detection - domestic smoke alarms are normally not suitable for commercial premises (unless of course you are talking about a HMO where in smaller ones they are OK) Not all Grade D smoke alarm systems can have call points added so knowing what exactly you've got would help. A proper fire detection & warning system to BS5839-1:2017 may be required if it's a commercial building.

Rough rule of thumb is one 13A rated extinguisher per 200 sq.m. (each extinguisher has a fire rating written on the front). British Standards (Guidance not law) cite a minimum of 2 A-rated extinguishers regardless of floor size, but that's overkill for the trades benefit and any competent risk assessor would be happy with just one if it's a particularly small office. As most environments have electrical equipment it's common practice to pair each fire point of water or foam with a CO2 Water Mist replaces the 2 separate extinguishers but not all extinguisher suppliers will stock these as they prefer the income from selling and maintaining (& replacing again every few years) twice as many extinguishers so you are best suited to order via Safelincs (don't forget to add Commissioning).

You will need a fire risk assessment and this will answer the questions - I'd need to see the site to give definitive advice.

It sounds like the vulnerability is where the pipes enter the roof void and this is the junction needing the most attention.

Yes, the door will have had it's integrity compromised unless installed with suitable passive fire protection products (e.g. https://envirograf.com/product/animal-door-flap/) and even then the door may loose it's cold smoke protection

You qualify for a free 'safe & well' visit from Royal Berkshire Fire and Rescue Service - their freephone number & email are on the below link: https://www.rbfrs.co.uk/your-safety/safety-at-home/book-a-safe-and-well-visit/are-you-a-resident/

Usually the communal system would have heat detectors and sounders in each flat to enable full evacuation, which is the purpose of the common system (if it had been purpose built flats it wouldn't need a common system unless it had smoke vents)

Has to be on the risk side (below). A full detection & alarm system to evacuate the HMO upon fire in the takeaway is a possible alternative

Kapok is quite nasty from a safety point of view: It is irritant: as the fibres are designed to disperse seeds on the wind, it is advisable to wear a dust mask when stuffing items with kapok, as the fibres fly in all directions and can irritate the lungs. It is flammable: the trapped air makes kapok highly flammable, and if it catches fire it is difficult to put the fire out. Special precautions are needed to transport kapok e.g. in the hull of ships. One advantage cited of this characteristic is that kapok can be used as tinder!