Upvote:2
According to Timatic, transiting UK without a visa is possible for: nationals of Indonesia making a landside transit with a confirmed onward ticket for a flight to a third country that departs before 23:59 the next day. They must:
have a common format residence permit issued by Ireland (Rep.), and
clear immigration, and
have documents required for the next destination.
https://www.timaticweb2.com/integration/external-result/olo-GnaVwj0nMAsfqkH40_cx3DUZ