When owning or purchasing a cross lease property, you own part (an undivided share) in the original freehold title, along with a lease over the particular dwelling purchased on the freehold title. The 'lease' is generally up to 999 years.
The lease will usually provide for an exclusive use area for each cross-lessee.
It's like owning a freehold property until you want to renovate, in particular increase the footprint of the current home. Permission to do so would need to be requested from the other neighbouring properties on the same cross lease.