Lifeboat stations in the United Kingdom
The state of UK lifeboat stations on OSM as of Nov 2018
Overpass Turbo returns 182 UK "amenity"="lifeboat_station"s
The official RNLI web site lists 238 RNLI Lifeboat Stations as of November 2018
Wikipedia has a (complete?) List_of_RNLI_stations in physical order around the country. Originally compiled in 2009 with frequent amends since. They do not have an entry page for every station.
Lack of Wikipedia entries means that a list from Wikidata will currently return an incomplete list ("instance of":"lifeboat station", "owned by":"Royal National Lifeboat Institution"). I used "owned by" to not receive data about other countries. However, it did show that there are some RNLI stations in Ireland/Eire.
The ESRI Open Data Portal RNLI Lifeboat Station Locations compiled in 2015 with help from the RNLI, updated in 2017. It lists 238 stations (the same as their web site... Q: are the two directly connected?) under the "GIS Open Data Licence".
Ordnance Survey have produced some tutorials based on the data.