Northern Ireland is part of the UK. It would therefore be quite appropriate to have UK military bases there. East Jerusalem is not legally part of Israel under international law. In fact, as the temporary military occupier, it is prohibited from seizing and building on occupied territory. The military can indeed requisition land temporarily for military purposes relating to the occupation, but it is a stretch of the imagination and law to include its national staff college as such, as it is not related to the military requirements of the occupation.
Report: U.S.-led strikes in Iraq, Syria killed 459 civilians (AP)
from the article: Haaretz probe: IDF base to be built in East Jerusalem