As a gatwick director, I do tend to bring the aircraft off early and have a long circuit. But this should always be flown at min stack and clean speed, I don't believe in early speed reduction or early descent.
If we are providing six mile spacing to an eight mile final, then tower asks us to 'pack' there are simply not enough aircraft in the sequence. i would say a 12-14 mile final is the optimum.(this also allows us to use speed control to refine the spacing). In my experience, a consistent 8 mile final is not the most efficient for runway utilisation.
In the summer mornings, there is a genuine shortage of levels in the two stacks. Gatwick approach controllers have a large amount of airspace, so by using that to have a few extra aircraft in the sequence, we remove some of the pressure for levels our terminal control colleagues suffer from.
we are not judged on delays ( in fact there is constant pressure from the airlines to reduce flow no matter the airborne delays),however it does seem more beneficial to let you fly straight and level for 15 miles west, then 15 miles east, than to let you fly twice round a racetrack pattern. Isn't it more comfortable ?
Finally, at heathrow, you can expect 180 kts from 25-30 miles out (through biggin in any southerly wind), 15+ mile final and 160 kts from as far out as 15 miles. Do you carry more extra fuel for heathrow than gatwick ?