I’d be putting a decent sign in sight from the Lot and on common property saying the exact unauthorized works are not included and are to be soon repatriated, with a suggestion all prospective owners be sure to have their conveyancing solicitor identify the formal Lot boundary and not take it as just what they are shown. It might also help to act as a prospective buyer and ask the agent to confirm such in writing, then it will likely be his head on the line as well as the seller. And acting as a interested neighbour visit the open house to be sure to ponder this aloud with other prospective buyers who would be interested in any intel they themselves would want to know before making any offer.