I have been saying this for years. What is the argument about using this facility?
The Airports Commission don't appear to have received your proposal (or anyone else's) for Heyford - there's no mention of it in their "Long Term Options" report.
Mind you, that £20 million would have paid for a fair few survey flights over Southern England, looking for existing bits of concrete close to motorways, if that was the only criterion required.
Or they could have borrowed a CAA chart and done it without moving from their desks.