Hello,
what is a daily temperature?
it all depends of room conditions... is it well insulated, how many rads, whats the area...
but setting it too low might create false impression of making savings...
anyways - you can try with optimization->optimum start where heating starts in advance to be ready with desired temp on the given time.
what I observe on underfloor heating it makes very little sense to lower night temp more that one degree. heating up in the morning takes too long.