For a time, ATC at Stansted allowed us to fly 170 to 5, yet it was scrapped. I would be interested to know why, because the 737-8 F5 speed is around 165kts! We are left with two choice - dirty up for the sake of 5 knots, or just fly 165 and hope so the best. Some guys at STn even recognise this and give us 165 to 4.