I've certainly heard of Severn Airways but I don't remember seeing any of their aircraft.
The Link City flights were almost always operated by G-ARAY, the second 748 prototype. Apparently, no other Dan Air base would keep this aircraft as it had unique wiring and other nuances. So, it stayed at LBA complete with its own manuals and schematics.
I recall Metropolitan operating the "City Link" flights on behalf of Dan-Air in the mid eighties using Sheds. After that the flights were ditched they were replaced by Capital. Right / wrong?