Lease extensions vary vastly. Some leases are virtual freeholds at 999 years others just an additional 99 years.
The cost of obtaining them covers a broad spectrum too. National Trust properties have their own particular rules and regulations.
So an extension was available but not the purchase of the freehold because it is trust property.
We researched the history of their occupation. Our clients met the specified criteria. They had occupied the leasehold house on a long term, at only nominal rent.
We successfully negotiated with the relevant National Trust department.