There is nothing wrong with getting someone to do work in lieu of paying rent. There is nothing wrong with paying people for doing work. You have done nothing provided you didn’t know that he was claiming benefits and not declaring any tax. If you did, you are potentially complicit with this fraud.
It is the person that receives the benefit that must declare it to the revenue and the benefits people.
You need to advise the benefits agency and the tax office. You can do that anonymously and tell them the circumstances and ask them to confirm that if you give the information about this person to them, but you will escape prosecution. They will do that. If they refuse, don’t give them the details.
Tell him what you are going to do. You can’t make the threat that you’re going to do it unless he moves because he may allege blackmail.
If he refuses to go, you are faced with making a court application for an order for possession and if, after getting that order he still refuses to go, you then make a further application to court for a warrant for possession for bailiffs to physically come and throw him out.
Can I clarify anything for you?