English farms can sell raw milk direct to the consumer provided they comply with very stringent health / processing regulations. It is not so easy to buy, therefore.
Helen Browning's Organic farms are near Swindon. Looking at their website, their milk goes to Berkeley Farms, who do not homogenise. It looks as though they have a farm shop.
Otherwise, I'd ask around at the Farmers' Market at Marlborough or similar. Someone will know of a dairy farm that sells their milk locally, in addition to Helen Browning. (Bishopstone Cheese uses her milk, or at least it used to when I was down there, and sells at Marlborough.) Hungerford might be a better bet?