It wasn't just Shacks.
When I took my son and my grandchildren to the Newark Air Museum we were privileged to get into the Varsity that they have there, which was the very first RAF aircraft I flew in (Fam 1 at Topcliffe).
My son's comment on getting in was "Do all RAF aircraft smell the same - this is how I remember the smell of a Nimrod?". (I took him and his sister on one of my trips).
The melange is exactly as described by sidevalve (I spent 7 years on Mk 2 and Mk3 Shacks).
The one element that sidevalve missed is, in training or OCU aircraft, is the smell of fear/stress, the fear of failure. This can be quite marked and once noticed never forgotten. I knew a chap whose wife could tell if there had been an "incident" during a trip, and when quizzed said it was the smell of fear! We've all been there at one time or another, haven't we?
The Ancient Mariner