Map source: Bringing Passenger Trains Back to the Waterside (pdf), Three Rivers Community Rail Partnership.In November 2017, Network Rail Infrastructure Projects conducted a pre-GRIP feasibility study (pdf) to identify and evaluate potential sites for a new station, named Welborne, to serve the new community. Four options have been identified and you can see the locations on the map below. Option 2 would occupy the site of the former Knowle Halt station, which closed in 1964 (see Wikipedia).
We are currently unable to explain why the feasibility study is “pre-GRIP” given that GRIP2 is named Feasibility. When more information becomes available it will be included here.