Question:
Do they all exist somewhere!? I would like to install some smoke,heat and CO alarms in the house, powered from the alarm supply, and connected to the alarm. I can find simple smoke alarms that will do this, http://www.tlc-direct.co.uk/Products/TLSD12.html but not heat (kitchen) or CO alarms that are 12v and have contacts for the house alarm. Any pointers?

Answer: -I'll need to check my catalouge, but you can get a "normal" fire alarm base unit that has relay contacts on it, and can put any of the heads, smoke, heat or CO2 onto it. I can't recall the name but I will find out.

-The following small circuit board replaces a PP3 battery in a smoke detector to provide for 12V operation with relay contacts. http://cpc.farnell.com/jsp/endecaSearch/partDetail.jsp?SKU=SR00543 These would probably not meet any BS requirements, if your system is required to do so. Also, make sure you test the detectors using the sensor after installation, not just the test button. They don't work reliably with the common rectangular EI smoke alarms (they do with the test button, but not with a real detector triggered alarm). Obviously, there's no interlinking, so you are dependant on sounders driven by the burglar alarm, rather than other smoke detectors generating additional alarm indications. I used a number of these in my house a few years back. The picture would imply the design is changed since I bought them -- mine have PP3 battery tabs soldered onto the board, and a changeover relay, and a jumper to select if the relay should lock on (reset by power interruption) or switch off when the alarm switches off. Another option is a 12V smoke detector (optical in this case) with contacts but no internal sounder: http://cpc.farnell.com/jsp/endecaSearch/partDetail.jsp?SKU=SR04245