Is this it ...?
This thread has been cracking me up - the creativity of ppruners never fails to amaze me !!
Have you seen the recent thread re: Newcastle / Gateshead (Helicopter activity NE UK ) ?
There are a couple of German Mil. Helis taking off from the pad next to the river which sound similar to what has been described over the previous 5 pages.
I must confess I don't know what they are (don't get out of the Ops office much and my window looks at a carpark !) ... but a possibility nonetheless.
Ps - LOVED the flying shed !! This is what the forums should be like - not slanging matches !!!