They wear a shirt and tie. No weapon. You don't have to answer the door to them. You don't have to let them in. However they are generally lieing scumbags who suggest that they are allowed in.

If they catch you watching TV they will report you for a £1000 fine and a criminal record. Failing to pay it will land you in prison.

I spent years without a license, you don't need one for YouTube and Netflix. I unplugged the aerial wire. You do need it for any live TV or BBC catch up TV. I got visited once during that time and he kept asking to come in, I kept telling him I didn't need to let him. He kept asking what I watch on TV, I told him politely, that was none of his concern.

If they suspect you are harboring an illegal TV then they will come back with a warrant and the police!