Sigh! Ah well I have been looking at the Transferwise conditions (as I will be moving the money to that account for best exchange rate to Euro first) and THEY will want proof of proceeds of sale under Anti Money Laundering legislation, so if BOI/Revenue/Man on the moon comes looking for it, it'll be there!
I think my initial worry was - I inherited this in 2015, now I get the money in 2020, do I need to let Revenue know, does it actually matter when the money is transferred , but I guess I will find out!