Ian:
The correct name is Tipping and Lawden I believe. Your Google searches might be more successful with the correct spelling.

You should probably try the Internet Gun Club web-site. I no longer visit there since they started demanding money, but that's probably my loss.

BTW, a 16-bore cape gun as you describe would be a marvellous general purpose hunting gun for the close stuff, ie pigs in the lignum etc. What is the twist rate of the rifled barrel? Set up for round ball, I'll bet. Congratulations on the acquisition, I'm envious!

It does sound rather short in the barrels for a BP gun, though. Interesting... Standing by for photos!