The British built a weather station/ radio direction finding facility on Malin Head in Ireland. Where they actively stationed troops.


Then there's the Cranborne report:

Viscount Cranborne, the British Secretary of State for Dominion Affairs, wrote a letter on 21 February 1945 to the British War Cabinet regarding Irish-British collaboration during 1939–1945:[48]
“They agreed to our use of Lough Foyle for naval and air purposes. The ownership of the Lough is disputed, but the Southern Irish authorities are tacitly not pressing their claim in present conditions and are also ignoring any flying by our aircraft over the Donegal shore of the Lough, which is necessary in certain wind conditions to enable flying boats to take off the Lough.

1)    They have agreed to use by our aircraft based on Lough Erne of a corridor over Southern Irish territory and territorial waters for the purpose of flying out to the Atlantic.
2)    They have arranged for the immediate transmission to the United Kingdom Representative's Office in Dublin of reports of submarine activity received from their coast watching service.
3)    They arranged for the broadening of reports by their Air observation Corps of aircraft sighted over or approaching Southern Irish territory. (This does not include our aircraft using the corridor referred to in (b) above.)
4)    They arranged for the extinction of trade and business lighting in coastal towns where such lighting was alleged to afford a useful landmark for German aircraft.
5)    They have continued to supply us with meteorological reports.
6)    They have agreed to the use by our ships and aircraft of two wireless direction-finding stations at Malin Head.
7)    They have supplied particulars of German crashed aircraft and personnel crashed or washed ashore or arrested on land.
8)    They arranged for staff talks on the question of co-operation against a possible German invasion of Southern Ireland, and close contact has since been maintained between the respective military authorities.
9)    They continue to intern all German fighting personnel reaching Southern Ireland. On the other hand, though after protracted negotiations, Allied service personnel are now allowed to depart freely and full assistance is given in recovering damaged aircraft.
10)  Recently, in connection with the establishment of prisoner of war camps in Northern Ireland, they have agreed to return or at least intern any German prisoners who may escape from Northern Ireland across the border to Southern Ireland.
11)  They have throughout offered no objection to the departure from Southern Ireland of persons wishing to serve in the United Kingdom Forces nor to the journey on leave of such persons to and from Southern Ireland (in plain clothes).
12)  They have continued to exchange information with our security authorities regarding all aliens (including Germans) in Southern Ireland.
13)  They have (within the last few days) agreed to our establishing a Radar station in Southern Ireland for use against the latest form of submarine activity.