Rus,
I'm a bit familiar with the Auster issue. You'll find plenty of debate on some of the other forums about this. To maintain a CofA there has to be a design authority responsible for the type certificate. If it no longer becomes possible to maintain an aircraft according to the type certificate, then the authorities may consider allowing them on a permit basis.
The approval costs are similar either way, though a permit aircraft may be able to use cheaper alternative parts if they are of suitable quality.
Some smaller permit aircraft can be maintained on a scheme administered by the PFA where the owner can perform their own maintenance under the supervision of an inspector, who signs off the maintenance release for the log book.
Permit aircraft are much more restricted with regard to public transport or aerial work operation.
I believe most Auster owners favour being allowed to go onto permit, but it's not unanimous.