We used to run an antique stall outside at Peterborough Antique's Fair and we found the Bargain Hunt team, a real nuisance.
While they were hanging about your stall, no one else was allowed near it. They used to re-arrange your stall. I told one of the experts off pretty sharpish when he picked up an item which was standing on the grass and placed it on a stool with a pale seat uphostery. No harm was done, but they would certainly have heard from me if it had soiled the seat.
Thankfully nothing on our stall interested them, but yes, they did try and bargain things down to ridiculous prices. They would have got very little change from us. The tv people seemed to think they were God gift to us and we should be delighted that we might appear on tv. Frankly, we had no interest in appearing on television.