I got a Christmas card from Newry area Northern Ireland today ( I'm in Dublin) that is post marked by the Royal Mail 13th December 2018 - well 13/12/18 to be exact. So it took 16 days to travel a distance of 100 miles approximately !
I'm in NI, family in Dublin and NI. Christmas cards between everyone seemed hugely unreliable this year, with some arriving in one day (even if crossing border, or second class stamps), and others taking an absolute age (even if just within NI).
I live a few kilometres south of the border, my daughter a few kilometres north, 6 km in all. I get a lot of post from Germany and it usually takes 8 - 12 days or longer to my Irish address, . I've resorted to using my daughter's NI address which takes 3-4 days. Sad but true. BTW: waves! Newcomer here, one year in Ireland, a few months on MN.