It's an outlet centre, that has been built around the existing Clark's factory store. The original Clark's factory and offices are next door.
To be fair, the motorway sign is probably because it's on the nearest "main" road. I used to have to fishy from Salisbury and it's an A road with tractor factor all the way.
Somerset is like Norfolk - things look a lot shorter in distance, but you have to factor in single carriage ways a lot so it takes an age.
Why was it disappointing? Not enough Brands? Try a McArthurGlenn or Value Retail outlet next time.