Owning a Share of the Freehold
The old alternative to commonhold is shared freehold in which the freehold is divided between the flat owners.
If you can buy the freehold, the advantage with this is that you can extend your lease at almost nil cost and you get control over the running of your building, so avoiding the problem of having inflated service charges imposed on you by a freeholder.
The disadvantages of shared freeholds are really down to the vagaries of human nature.
Just as in commonhold you'll have to get agreement from others about maintenance. This can be difficult and especially so if owners do not live at the property. Also, some people can be just plain difficult or even aggressive - which is not nice especially if you have to see them regularly!