….. the smoke sensor is 59GBP and the motion sensor is 50GBP in the UK so around $80-$90 here in the USA. I have family in the UK so if we know they would work may get one shipped here.
You’d better think carefully about that…
Z-wave devices in Europe (including the UK) operate on a different band to US Z-wave devices (868.42 MHz for Europe vs. 908.42 MHz for US). Therefore Z-wave devices made for the European market will not communicate with a SmartThings hub built for the US (and vice versa). We have a similar problem here in Australia (and New Zealand) where Z-wave operates on yet another band - 921.42 MHz.
This is perhaps the biggest failing with Z-wave - it adds substantial ongoing overhead for manufacturers trying to supply multiple markets (over and above the different certifications required) and results in significant market segmentation.