I have flown in Europe a few years ago but not sure where you are referring to. Northern Italy descending over the Alps?
Why not bring the speed back to min clean while you are being kept up then dump gear/use speed brake and accelerate back to 250kts when cleared to descend.
The flap 40 trick works well but I only use this closer in as it stuffs up traffic flow! I need speed about 155kts with flap 40 at higher weights on the 800W to achieve 1000'/nm.