Here in Wales we are in a similar position in that there are literally hundreds of semi-collapsed dwellings/agricultural buildings in the landscape. The majority of these are on agricultural land and therefore do have legal owners; other examples are on common land. All of them are fascinating.
There is a problem, though, with the restoration of a lot of them because of planning policies. Generally local plans allow for new houses, barn conversions and renovations on the fringes of villages; however, in areas of outstanding natural beauty, national parks etc, there are policies which aim to keep the areas unspoilt, and thus discourage renovations of isolated buildings. As planning law stands at the moment, if one isolated ruin received planning permission for renovation/conversion, it would then be possible for someone to put in an application to build nextdoor to it, and before you know it, the beauty of the landscape which attracted people in the first place would have become blighted by residential sprawl. There is an area about 40 miles from where I live which is stunningly beautiful, but the local authority started allowing development in the open countryside, and now large areas are blighted by rows and rows of modern rectangular bungalows.