If you Google Shepherds Huts there are lots of people making them. One of the best (and priciest) is Plankbridge in Dorset see http://www.plankbridge.com/
But of course this is a long way from you and transport would add to the cost. Also, it would be good to get one of a design which was common in your area, as they do vary a bit.
There's a growing interest in these over the past few years, which means more people are making them, but at a price.