Ultimately this is the most important story in British politics and much of the world - the Iran war is putting pressure on real wages, which people will blame on the incumbent government.
You don't have to answer the door for the Feds. Do not voluntarily talk to the Feds. If they have a warrant signed by an actual judge, then they can do precisely what the warrant says.
But DO NOT TALK TO THE FEDS. Do not answer the door. If you're arrested, your only words are "I want a lawyer."