Not surprised the Jacobean Lane one has not gained approval. The Lawsonford one does not seem a great location either, it impacts on a small village, and the canal location puts in amongst a large number of locks, so increased boats will have a bigger impact.
I would hope that the Stripes Hill (bottom of Knowle locks) one would get the go ahead. To me that is a much more suitable location, not near housing, good road links, and the land is low lying wet land which is not great for agricultural use. The canal location gives access to a sizable pound from Knowle ot Hatton.
Living in the area I would say that there is a shortage or marinas, ie there are basically none of any significant size on the GU until Napton, and nothing on the Stratford at all.