Treaddur Bay? That almost sounds like me... a depression I am not, mountainous is a better description...
Damien, someone posted a good story about a Gnat prang at Valley on this very forum - IIRC an unoccupied MB (I think?) just missed the Rescure Whirly. BEagle was it you recalled it?
I recall seeing the Sparrows at Middle Wallop in the last Gnat season, '79 - the singletons have left a lasting impression of being below me at one point... long time since I've been to Wallop, but below me? Surely not...