Thank you Andrew (and a Happy New Year to you) for the knowledge your experience brings. Generally I'm not fond of battery powered devices as part of core infrastructure, but I will definitely consider z-wave devices for adding to the system that I already have planned.
(An aside) Interestingly (or not) spending a bit of time on here and just getting feedback has led me to consider using LinuxMCE exclusively as my security system, and dispensing with the comfort alarm panel. I don't envisage needing the alarm for external validation, but more for my own purposes. I think the comfort may be unecessary for me, particularly if I can wire alarm sensors directly to the core and use KNX integration to trigger events (like room PIR senses an occupant, and if it is after sunset, the lights come on, etc.).