First off, 20 Soay on not much more than an acre is way too many, so yes, they need to go. Finding someone who will take that many unregistered wild Soay is going to be difficult. Ideally, they would go to someone who can handle them and fatten them for slaughter, maybe to sell on to a restaurant, but finding such a person is the problem. Because Soay are quite small, an everyday butcher wouldn't be interested and because they are unreg and not an ideal weight, wormed etc, the RBST meat scheme will not be interested.
At the large estate across the valley from us, the game keeper there has a license, plus cool facilities to kill and handle game. Soays are the next best thing to game. My thoughts are creeping towards a shooting estate looking for a novelty prey for its punters to come and shoot. I know someone who always passed old Jacob tups onto the estate next to them for shooting.
However, I have no idea if you have shooting estates in Cheshire or roundabout. The Pennines? In that situation I'm sure they would collect them from you.
Just some ideas. Maybe someone on TAS is interested or knows someone who would be.