I remember that one too. I think they might have been inside a dinosaur.
Just watched that episode. Yep, it was an unusually large and well-preserved T-Rex they found in a cavern under their apartment building. They got trapped inside and lived in the stomach for six months, until they accidentally revived it.
This used to be on PBS (Boston's Channel 2) in the 1970s. Channel 2 was showing a lot of imports around that time including Monty Python, Dave Allen at Large, and The Two Ronnies.
Dave Allen. I used to love that show. Back in the 80s, one of the stations we got ran Benny Hill and Dave Allen back to back every weeknight. Probably the only hour of TV my dad and I could enjoy together. He usually only watched news and sports, but those two shows cracked him up. I actually had the good fortune of seeing Dave Allen live on stage when he was touring Canada around 1990. When he wasn't toning it down for TV, Allen's standup routine was even funnier.
I remember The Two Ronnies from around the same time you do. Probably the same PBS broadcasts, just a different affiliate. Nobody else was showing British TV in North America at that time, to my knowledge.
There were quite a few British shows I only caught a glimpse of as a kid. The Two Ronnies, The Goodies, On the Buses, Kenny Everett in the early 80s, and the actual Monty Python series. Thanks to the movies, I saw more Monty Python growing up. I don't think it was until the late 80s and early 90s that a lot of shows were imported directly. In the 70s, if a show was big in Britain, American networks just based their own show on it, giving minimal credit to the source. All in the Family, for example.
Come to think of it, I wouldn't mind checking out 'Til Death Do Us Part. I've never actually seen it.