It is not unknown for a developer to buy a property or properties at the head of a cul-de-sac and demolish them to access land on the other side which has been hitherto landlocked.
Your situation is not too dissimilar although he is not demolishing houses.
The reality is that because you signed contracts which allowed this, there is very little you can do about his proposal except with regard to objecting to the planning application on the basis of the adverse effect on your property and the increase in traffic over the narrow road and the dangers involved.
Presumably, 5 people will object and the more objections are put forward, the better.
I would suggest you use the planning consultant to put your objection forward because they will have a better idea of how to word it.
If all 5 houses pay towards the fees for the objection, it is not going to cost that much between each of you. However if one of them does not contribute, they will still have the benefit of any outcome.
Can I clarify anything for you?
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