Orangewing. According to my mates at Luton, traffic has to be uniformly delivered to the tower by radar due to the nature of the backtrack problem on both runways. A stabilised approach means judging the ‘gap’ between successive inbounds is much easier and straightforward and reduces the risk of a go around it also ensures that a gap created by radar is not eroded.
160kts between 7 and 4 mile is used usually when there is no other speed restriction, so you can fly as fast as you like up until that range.
May I suggest you visit the VCR and West Drayton; all will become apparent once you see what those guys (And gals) do.