That's not the way to look at it. If a suitable person can get the approval you need, then can you afford not to use one?
Pay someone then skimp on the internal fit while you save up.
But only pay for someone that knows what they are doing.
Or do more research on policy and design and submit your own plan. Include a design statement, and pretty 3d drawings from the street scene to show that there is no terracing.
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