I've been listening to a pair of Graham LS 5/5s for almost a year. Before making the purchase, I compared them with the 40.3xd directly at a dealer who has both brands. The dealer put down painters tape in the room and swapped the speakers in and out at about 30 minute intervals. The Grahams had the matching stands and Gaia footers. The Harbeths were on some type of steel stands, not sure of the brand.
The speakers sound more alike than different, not surprising given their BBC heritage. Great midrange, everything is just the right size - neither too big nor too small, unobtrusive treble, no listening fatigue. In my demo, which was conducted in a very big room with concrete floors, I thought the Grahams were noticeably better. They had more resolution, greater depth of image and clarity with no drawbacks. By comparison, the Harbeths sounded a bit smeared. Maybe it was the Gaia footers - those are the kind of improvements that I would expect good footers to make. FWIW an employee who used to work at Gig Harbor Audio told me he agreed with the assessment.
PS: if you read the previous thread comparing Harbeth 40s to Joseph Audio, you might be interested in Christian Puunter's take on the Graham ls 5/9 and 5/9f. I think he gives a pretty good description of why some people really like the BBC sound and others prefer "higher end" speakers such as Magico, planers/ribbons, etc. Different strokes…