LG-
Purdeys are nice, but a lot of them are all the same. I think they're a bit plain and boring.
On the Lancaster, I don't know why the front lump has an extension on it that comes through the floor of the action.
Here's a Lancaster boxlock O/U:
http://www.connecticutshotgun.com/guns/3755.htm I think this gun was made up in Germany and then finished off in the UK by Lancaster. I remember an article in the DGJ about Lancaster doing this.
I wonder if part of the sidelock O/U had origins on the Continent as well?
A lot of European O/Us are like that (lump extension through the action), so it would make sense.
Check out the lump extension poking through the bottom of this gun:
http://www.connecticutshotgun.com/guns/3135.htm OWD