Hmmm interesting katy.
Although, in this case it seems that they bought it when they were an allotment society and have since ceased to use it as allotments, so basically they're just a group of people who co-own a piece of land. I'd say they're probably legally entitled to sell it.
On the one hand I think it's a crime that allotment land is being sold left right and centre for housing, but on the other hand this land isn't currently designated as allotments so nobody's losing out?
kitten x