Many of the operators were inter-connected, I understand.
EOS were part of Swallow Coaches.
Roadrunner and Olympian were part of Olympus Bus & Coach, itself seemingly linked to Townlink Buses (previously known as SM Coaches).
Indeed, Roadrunner/Olympian/Townlink/SM Coaches were all inter-connected, and your typical 'cowboy' operation. A few run-ins with the TC helped get rid of those (eventually).
EOS were indeed part of Swallow Coaches, and was a pretty decent operator. They put a lot more effort into publicity and Twitter than any of the other operators. It was a shame to see them go, but it was their own decision to cease operations. The EOS contract routes (Essex CC) are still operated by Swallow.
Trustybus is part of Galleon Travel. A few years ago they sold the Trustybus operations to Centrebus, but they failed to make a success of it. Then Logic Transport started (which was sort of related to Galleon, I think), which eventually became Trustybus again.