Finally, finally got my interdiction. Had been trying for ages, gave up a few times. Decided to go ripe barnacle hunting and it was on the jump into a known ripe barnacle site that it happened.
Given this, and the way it played out, I couldn't help feeling the flowership was telling me to stay away from the barnacles. I can't shake the feeling that any ships near ripe barnacles are soon going to be toast, and if you've mined them you could be on their hitlist.
I'm probably wrong - it was 4.00 in the morning [wacky]