Security lights not turning off after 2 mins

Have I gone about this the wrong way?

Your 2 minutes off is also with pending cancellation. Since you did not post the whole rule. I would take a guess and think because the motion was still active or triggered again inside the 2 minutes window.

Only seeing the action part of the rule or trigger or triggered rule won't help. You have to post a screenshot of the whole thing in order to debug what's happening.

Sorry, i was trying from mobile, desktop version attached...

You have the run actions still hanging out there. You should remove that. I'm suspecting that the timeout for your motion sensor occurs canceling the off function. Either remove the cancel or put the off into the false part I'd the rule.