I guess it will be impossible to measure but was surprised at LGW last week. Boarded a First Choice flight to Kos out of (I think) Gate 55. If you look at the picture in the link, the boarding area is just to the right of the last of the three widebody jets, and the aircraft is to the far right!
http://maps.google.co.uk/maps?hl=en&...wloc=addr&om=1
Mark