There are quite a few sitcoms which aren't available to stream and which never got a DVD release. Piracy is the only way to watch them, and often that means poor quality captures.
This is the start of a list of such shows. I'll add more as I find them.
According to Bex - https://en.wikipedia.org/wiki/According_to_Bex
All About George - https://en.wikipedia.org/wiki/All_About_George
Having it Off - https://en.wikipedia.org/wiki/Having_It_Off
That's Love - https://en.wikipedia.org/wiki/That%27s_Love_(TV_series)
Heartburn Hotel - it sounds awful, but I'd like that to be my decision. https://en.wikipedia.org/wiki/Heartburn_Hotel
High Hopes - https://en.wikipedia.org/wiki/High_Hopes_(British_TV_series)