As X-10 uses the power line, which I believe on your side of the pond is called the mains, to send signals and Z-Wave uses RF, it would seem that there would not be a problem.
For a more informed reply, instead of my guess, you might go to
[Link: z-wave.com] which lists 3 or 4 forums on which Z-wave is discussed. On my monitor, which I need to replace, the blue text to click on does not look much different from the regular black text.
I just took a brief look at some Z-wave modules which seem to be priced at about double the price of X-10 Pro modules. If Z-wave is reliable then at this premium it is a bargain over X-10. It is interesting that there are some pretty large companies making Z-wave devices.
I have been using X-10 for about ten years and almost every switch in my three bedroom house uses the X-10 protocol and I have had to add a repeater, a coupler, boosters, filters for devices that put noise on the powerline, and worry about signal suckers.
And while my system works fairly well, it took a lot to get to that state and I sometimes have lights that fail to turn on or that turn on for no reason. I expect that if I had a wife instead of living alone, my X-10 devices would be in a landfill by now.
Cheers, Jim.
