Tony, the 'Companion' tubes are (as far as I can tell) a 12 ga only product. They are a non-fitted alternative to more expensive fitted small gauge tubes.

Briley can no doubt fit a tube or liner, as can probably Teague on your side of the pond.

The bad news, of course, is that tubes make the barrel set quite a bit heavier and are sure to change the dynamics of the gun significantly.

Unhappy incident.

"The price of good shotgunnery is constant practice" - Fred Kimble