Hi Again Will,

Wikipedia is hardly authoritative but the following was interesting:

"Interestingly, a statistical study on 565 works of art of different great painters, performed in 1999, found that these artists had not used the golden ratio in the size of their canvases. The study concluded that the average ratio of the two sides of the paintings studied is 1.34, with averages for individual artists ranging from 1.04 (Goya) to 1.46 (Bellini).[22]"

Source: Golden Section and the Art of Painting

Authors: Agata Olariu (National Institute for Physics and Nuclear Engineering, Bucharest Magurele, Romania)

(Submitted on 18 Aug 1999)

http://en.wikipedia.org/wiki/Golden_ratio
Also this PDF is interesting:

http://www.umcs.maine.edu/~markov/GoldenRatio.pdf
Cheers,

Sean