There are a few overt P6 smells:
1) Leather. Depending on the colour of the seats and the age of the car they can all smell very different. My 1964 2000 smells exactly like a shoe shop - it must have been the process used on the hide. Late 1960's car have that 'bottle it' Rover smell that you could sell to like minded Roverheads if you could do it. This is, I suspect due to who supplied the leather. There was obviously more than one supplier etc.
2) The smell of death - rotting underlay from water getting in courtesy of developing or rampant rot. Once it's in a car it's difficult to move it, hence why a lot of really good looking and well restored cars still have the tell tale acrid aroma when you get into them.
3) Another bad one - fumes coming into the car from the engine courtesy of the heater foam being fubar. I really don't like this one at all, and far too many cars I've driven have had it. Not so much a smell, more like a really nasty sensation of bad air.
4) Fuel smell - later cars with the different breather tend to really stink for some reason. Anything over half full and the overpowering smell of petrol is really annoying, and worrying. I suspect this is, in a lot of cases, due to pipes being cut/moved during welding as my 2200SC does not do this, despite being a pretty late car.
5) Waxoyl. My 2200 absolutely hums of the stuff as the previous owner filled every nook and cranny he could. I don't mind
That's not including sweat/tobacco etc. etc.
