Probably another case of someone telling you something they think you want to hear. Why is there no cable in Weston? Because the company that originally won the franchise to build that part of the network went bust before the build was completed. The vast majority of the build out from the Aztec headend (Bristol & Bath) was however completed, so you are not far away from the existing network infrastructure.
So the best course of action for now is to register with CableMyStreet, & keep your fingers crossed that Weston gets added to the areas now being installed using the new RFoG technology.