We do (council property, legal requirement to have a mains fire alarm and CO2 detector) Don't actually need one though as the Boiler is new and (apparently) a sealed system, so should it start leaking CO2 it'll vent straight outside.
Rather scarily though, I discovered that accidently leaving a plastic chopping board on the hob whilst the oven's on, releases enough toxic fumes to set the alarm off!
Yes. We've always had those little stick up patch things in the past but the boiler is in the loft in this house so I bought an alarm.
I've moved back to the area I grew up in and live about 3 or 4 houses away from the house my best friend grew up in. We both vaguely remember an elderly couple dying from carbon monoxide poisioning in one of the houses .I'm not sure if it was mine or my neighbours as although it doesn't put me off living here I'm not sure I really want to know for sure! Whilst it isn't really relevant as you should be careful in any house, I bought a battery powered one the week we moved in.