On a slightly different but related topic and only in Scotland so far.... from Feb 2022 the regs on detectors are changing. All smoke, heat and CO detectors should be interlinked plus there are some other details which you should check.
Suggest you re-read the document. Only smoke/heat detectors need to be interlinked - CO detectors do not need to be linked either between themselves or with the fire system.
Interlinked smoke/heat detectors have been available for years - we've had them since we had a kitchen extension built in 2017. I think the pair cost about £24.
PoI: caravans come these days fitted with smoke detectors, usually the Fire Angel variety, but the caravan manufacturers persist in fitting the cheaper smoke/heat variety which go off every time you even think about burning the toast, rather than the rising heat type which do not. Thankfully if you replace the former with the latter they do fit the same base plate.