Thanks for all the information in the replies, I have to admit that some of it went over my head slightly, however the analogies of the cookie cutter and the ever decreasing spiral struck home. I also share the view that this is all about the vision and mastery of the tools is important in order to achieve that vision.
Going back to the ever decreasing spiral analogy... my camera is set to encode the captured images as AdobeRGB (Canon 40D) is it then not a step up, an increasing spiral (or a stretching out of the cookie dough) to then display the images in lightrooms version of ProPhoto RGB?
Another part of the puzzle that concerns me from a technical view point is the increased posterisation that occurs when the same number of bits is used to encode a greater range of colours. In practice is this a reasonable justification for shooting in the same colour space as your final output? Although, I print in sRGB today, there is no telling what I could use in the future, so perhaps this should read as shooting in a colour space most suitable for the image you are taking?
I will have a play with the gamut warning feature this evening and see what that teaches me.