You cannot get pre-planning advice for this kind of development in a week.
An Outline Planning Application would cost about £10k just for the application fee. You'd pay half again for some proffessional fees to do some drawings. And that's assuming no other environmental reports, tree surveys etc etc would be required, which they would. And people wonder new houses cost so much and every last penny is pinched.why not apply for planning permission to put some nice houses on it, then sell with that permission in place.
For planning permission, you can provide a pretty basic drawing, so long as utilities, access, roof plan etc. is shown, they can make a decision ... I think. I did my own extension plans, a small development must just be an extension of that.
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