I've been very happy with the evohome heating system so I'm considering installing the evohome security system and ditching the existing alarm (which is elderly and needs several changes). Any experiences of it, especially the door/window sensors? The reason I'm particular interested in the sensors is that I want to modify them so that there is one per window position, but modified to allow multiple n/c reed switches (one for each opening window) to be wired in series with the one that's built-in. I haven't bought a sensor yet so don't know how easy/hard it's likely to be to open them up.