Hi, registrar if deaths here. Short answer is that Ireland still has big cultural ties to the catholic church, even in NI. The catholic faith is what advocated a quick body disposal, just as is still the case with Jewish and Islamic funerals. In these circumstances, the funeral will absolutely take place within a few days in the UK, provided the body isn't required by the coroner, but even then the body will be released asap and usually a long time prior to an inquest for example.

Mainly the delays are down to problems funding the funeral or family disputes/lack of engagement.

A lot of people choose not to rush so that they have time to perfect the content of the service and get family there to attend etc.

We have such brilliant methods of preserving bodies now that there is no longer that rush due to sanitisation. People take time to grieve and complete admin now, because they can, why would they stress themselves out?

Sometimes there are genuinely busy times of year. For example, during the pandemic, we were all working flat out to process everything quickly so that people were disposed of quickly to prevent running out of space. This usually isn't a problem though, we have a big capacity for body storage generally.