Cork Airport
The problem at Cork is that the authorties seldom seem to know in advance whether CAT 2 will be required. Neither are the MET MEN able to predict with any accuracy when the weather is likely to improve. How many times over the years have aircraft on approach been told that the RVR is below limits only to discover a major improvement by the time they get here. Similarly the weather closes in with little or no advance notice.
The Ryanair would probably have continued on to STN if the weather came down again and who would put money on it not happening now that the moist atlantic airflow is back again.
Airlines won't risk a second diversion with the same aircraft as most of them know Cork all too well.
Of course there was nothing stopping the authorites from going CAT2 in anticipation of a disimprovement in the weather.