It should be noted that in addition to Luton's current field an area approximately 2 miles by 3 miles lays flat, south of the current runway! Plenty of room for 3 or 4 runways.
I estimate less than 100 dwellings would have to be moved.
Change the runway headings to 09/27 then Stevanage town and Caddington would not have to be overflown.