MN is always half full of people saying you need to stand up for yourself and the other half telling people to roll over.
It’s ridiculous that you wanted an allotment and now you have one you can’t use. If Barbara had any critical thinking skills she must have known this was an option. If this was her dear friend they she should have know she was selling/leaving.
Our family home had a stretch of grass down the side, it wasn’t fenced off as part of the garden because of height difference, then there was shrubbery separating it from the path. We played down there a lot as kids pretending it was a den.
When I was a teenager the house next door was sold, and they put a caravan on it. My dad told them to move it, they said they only bought the house as they thought it was theirs. As my dad said why would you even think that, gave him an hour to shift it and fix the fence they had moved.
Just because you want something and might find it useful, doesn’t mean it’s yours.