Ford Focus 2.0 TDCI, 56 plate.
I spent most of yesterday taking off the engine undertray, taking out the glovebox and fusebox, removing the radio and surround only to find that the annoying vibration I've been getting for the last few months was from the heater pipes vibrating against something, I don't know what, but what I do know is that if I put some foam between the pipes, the vibration stops.
I found this photo on the web (originally from this site) If you look at the 2 pipes to the LEFT of the red circle (they are almost horizontal), these are the offending pipes.
I couldn't find a mention of anyone else finding this particular vibration spot, so I thought I'd post it.
P.S. If you find a solution to a question you have asked, please report back and help others