[hackeraccount]

Maybe. It would depend upon just how much the Irish government was supporting the IRA. What if the Irish government was backing the IRA to the degree that Iran supports Hezbollah and Hamas? If that were the case don't you think the UK would respond in the same manner?

Honestly the Israeli response (killing Iranians in a third country) is probably more restrained then the UK would have been. I expect the UK - in a hypothetical world where the Irish had supported the IRA to the degree that Iran supports Hamas/Hezbollah - would have struck Ireland directly and not offered even implausible denials that they had done it but instead trumpeted that fact.