I ask because living where I do I need to plan for power cuts. They are not frequent, but they will happen, and when they do it is quite likely to be during 'interesting' weather.

I know the 'slug' is only rated at 10W and I do have UPSs, but it's not unusual to have at least one extended (i.e. 6-8 hours or greater, 24 hrs is not unknown) power outage a year here. Even if there isn't an 'accidental' power cut of that length there will almost certainly be an occasion when the power company pre-arrange for a cut-off for most of a working day to allow for essential maintenance[1].
I've skimmed through the manual and appreciate that the WMR200 logger interface details may not yet be available, but other software (e.g. WeatherDisplay) is handling logged data, so maybe that availability change?
[1] We near the end of a 15 mile 'spur' so maintenance, or a new supply, anywhere along that length requires the whole line to be disconnected.
David