Terrible news. I hope that something can be sorted out. OSFC was in my experience a unique organisation and an example of how club flying can be made fun and challenging for all experience levels.
With regards to house building, Old Sarum Airfield has Conservation Area Status because it was considered to be of considerable value in terms of cultural heritage, due partly to being in constant use as an airfield since 1917. The hangars are also listed buildings. Given this protected status I don't see how anybody can plan to build houses on it. Anyway, aren't the houses being built across the road?