Not sure if it's a goer with all the regulations etc but what about an online shop where people search for what they need (eggs, ham, half sheep, veg etc) and add their postcode. All of the members on here could put their products that they'd like to sell on the website and also add their postcode, and you could take a percentage of all the sales. Maybe a good way of connecting customers with small holders who aren't big enough for their own website and advertising.
All the TAS members could effectively be a giant co-op.
Just a though...