That is the word that goes around......HOWEVER, neither Lasors nor JAR FCL 1.155 specify that it must be done on the same day.
What if the trip was done overnight?
I think the test of 'what is reasonable' needs to be applied.
If you left Cardiff at 1800 and flew to Waterford, then later flew up to Dublin or Belfast and returned directly to Cardiff the following morning arriving at Cardiff by 0600 I would have thought that would be perfectly reasonable and acceptable. It would in fact be more demanding than carrying out the same trip, leaving Cardiff at 0600 and finishing at 2200 on the same day.
On the licence application form you have to state the date of the QXC. The CAA officer handling the application will check your log book on that date. If it showed the above I couldn't see it being a problem.
The people to ask are........drum roll........the CAA!!!