Have a form control , built in property > Description , how do I control its permissions at block level as don't see any permissions options until after page is created. It seems that it takes it from Area permissions.

This is the set up for page owner
Page permissions taken from Page Type permissions (allow edit)
Area permissions taken from Page permissions (allow edit)
3 blocks in area , 2 of which are manually configured to Not allow edit
Third block which originates from a form control ( built in property > Description) should allow edit but does not.

Update ******
I decided to separate the form control ( built in property > Description) into a new Area called Description. This area has by default "The following area permissions are inherited from the page's permissions." which gives the results as full edit on block as well as Delete etc ( see attachments ).
However I don't want Delete just simply Edit , so I change the Area permissions to "Permissions for this area currently override those of the page." which has exactly the same set up ( see attachment ). but when trying to edit I now only get Edit area design and Add Layout but no Edit ( see attachments). So I still come back to the possibility of setting permissions on a form control ( built in property > Description).