I've been looking at this at gun on Holts as well, and the styling of the breech block where the barrel 'clicks' in, and the inclusion of the screw to retain/locate the breech/rear air cylinder plug is shown in a photo of a double spring clip MK1 on page 16 of Gordon Bruces 'Webley Air Pistols' book. Sadly it doesn't show the serial number of that gun, and yes, the spring clips are different, having the 'dimples' that would push against the barrel. But the photo at least shows a MK1 double spring clip with a similar set up to the one on Holts site.

Where it has been said in earlier posts that breech is broken, could anyone please point out where, as from the photos on Holts site I can't see any damage to the gun.

Many thanks.