Wouldn't this be a nice spot for a Shepherd's hut. The post was looking a little dull, so I thought I should put something in! This is my sister's land in Maine.
A "Tiny House" is simply a shepherd's hut that is meant for full time or long term living. They can be the same shape and size, though most "Tiny Houses" tend to be cut up into a warren of rooms for different uses, and a shepherd's hut tends to be mostly one big space. The "Shepherd's Hut" tends not to have loft space, though there are no rules.
Ordering one of these from the builders in England or here in the states can be expensive, mostly over $25,000.00 judging by what I have seen, for a simple hut, where the more elaborate ones can be upwards of $60,000.00 and tiny houses can be more, as more materials and labor are involved for long term living.
Of course, it is possible to reallocate space later on as I use the space. In fact this might be a good idea so you get a feel for what you need, which is often much less than you think.
Thanks Wikipedia for these three photos.