@Donald McCraig, we train once a week for about 3 hours during which time he works about half an hour in total. Outside of that, he gets a walk most days and some hide and seek games too. Thanks for the feedback, it has given me a few things to try. Interrupting the behaviour is difficult, but I've got a few ideas. If there are any more suggestions or stories, I'd love to hear them.
I rescued a stray border collie x a year ago who has been a delight to have and is almost 6 months into his training as an urban search and rescue dog. He is progressing very well and is 2.5-3 years old. Three weeks ago, my husband was using his laser measuring tool inside when the dog kept chasing the spot. It was a bit of a laugh and it got put away. He kept looking for the spot and eventually stopped. This was, however, replaced by staring at lights, light fittings and reflections on the walls every time he's inside. He's massively distracted, staring and waiting for something to happen