I thought this was the one the Military used....
Aircrew Map of Great Britain
Not seen that for a while! I know Sally's Tits as a pair of pointy hills north of Welshpool. And 'X' (Piss off Biggles) was painted on the roof of a barn in Wales by a farmer fed up of low flying fast jets. Of course word got round and everyone out for a blast included the farm in their itinerary! I understand it even features in the Valley Hawk sim!