This is as true in the US as in the UK. If you want to ensure products that are not on the compatibility list are going to work you are going to have to create the devicetype yourself, just like we do stateside. If your not up to code, then you probably don’t want to stray too far from this list.
http://www.smartthings.com/uk/compatible-products
Yes there is, its called z-wave smoke alarm and there is nothing in it about frequency, just commands, and most of the commands are the same among the same class of devices.
Same issue in the US, the switches just aren’t as common but a community created a devicetype for it and it works well.
I had this problem at first too… then i got better batteries… So far the Energizer ECR2032 have lasted the longest.