Watching TV on the internet
You need to be covered by a licence if you watch TV online at the same time as it's being broadcast on conventional TV in the UK or the Channel Islands.
That means you can legally watch iPlayer shows as long as you don't watch them as they are being transmitted. The burden of proof would be on them to show that you did otherwise. To do that they would have to confiscate your computer and to do that they would need a search warrant.
I never watch TV shows live on the iPlayer.