yours2share gets mentions and links from many and varied forum posts, but I had to have a look at this forum when I saw the link on the stats pages: PigeonWatch. The forum entry is actually about sharing allotments, but I was intrigued to find this forum devoted to pigeon shooting. With nearly a million posts this is a thriving forum.
As the post indicates, yours2share has lots of ads for land sharing (garden sharing or allotment sharing) as well as guidance.