responsibilities
It has long been established practice that previous colonial powers are duty bound to previous colonies to provide them with certain services or facilitate their use. There is no law or treaty controlling this but it is recognized proper international behaviour.
This duty is often seen in ambassadorial, finance or military assistance modes.
For instance the UK provides flight training and military officer training for many ex colonies. We loaned Ireland a large sum of cash when it had problems during the finance crisis and so we should not be surprised when this assistance extends to other crisis situations,
The RNLI remains a single rescue organ covering Ireland and the UK. It suits us to be of assistance to nearby countries because it obviates their need to seek aid elsewhere.