Over the past few years we have successfully stopped a develpoment of a detached house in a garden next to us. The applicant then changed the permission he sought to an extension to his own house and we did not object, He received planning permission for the extension and then immediately posted a new application to change the extension to his house into a separate dwelling. He has been granted permission to build this semi detached house. Surely this is an abuse of the planning system, It is obvious he had no intention of building the extension and was using the planning system and deceiving his neighbours.
I don't really see your point. each planning application is judged on its own merits . Whilst you may have had an objection upheld to a particular development proposal that was considered unsuitable it does not mean the site is permanently sterilised. There can be a world of difference between a detached and sem d house in this regard.