As Miller pointed out, you do need to be careful with British vs American velocities. The "observed velocity" measurement (avg over 20 yards) was the standard a century ago. Much more recently, back before I understood that difference in their measurements vs ours, I ran across observed velocity figures for Eley shotshells in Gough Thomas' books.
Currently, however, they will often use muzzle velocity. But unlike our muzzle velocity, which is measured at 3 feet, theirs is measured at the muzzle. So if you see British shotshells with pretty high velocity figures--like 1400 fps--you can be sure that's MV and not observed velocity. And would likely equate to something less than 1300 fps as we measure MV. A load loses a bunch of velocity in that first yard.
