Self and Custom Build plots on s106 sites - Public forum - Planning Advisory Service (PAS)

What % of occupied open market dwellings are authorities allowing in their s106 agreements before developers have to market the self and custom build plots? Also are authorities preparing plot passports and design codes for plots on s106 sites or do you consider it to be the responsibility of the developer? 

We keep being being challenged on both of the above issues at the moment so it would be really helpful to get a view on what others are doing.

Thanks in advance.