Hello Gordon, thanks for the comments. I have searched every site i know of and cannot find a comparable review between the 17-85 and the 24-105 so its good to see the comments you mention.
I have a 17-40mm l series lens already which I find an excellent lens at its 17mm end but does not give me the reach at the 40mm end. I agree the l series lenses are excellent in build quality and for this reason am looking at the 24-105.
I am hopefully going to try one out today on my 350d so will see how it performs at the 105mm end.