If you have a nearby livestock market then put them in there on the day they are selling store animals, NOT in the fatstock sale. That way they will be bought by someone to fatten further. You will get as good a price in market as anywhere.
I personally always stand near my pen of animals before they are sold, or even go in the ring with them, then you can tell prospective buyers about them and they might get a better home from someone who cares where their animals have come from.