Handle9:
The gas contractor may be gone (or may not). IME for services the council relies on the certifying contractor rather than inspecting everything themselves - building inspectors aren't competent to inspect services, they don't have the expertise. If the installation is certified as compliant (in line with the regs) then that's generally enough to get COC.
CCC.
Yep. Another issue may be whether a gasfitter actually needed to issue a formal CoC in ~2008. I suspect possibly not, Gas safety regs changed in 2010, but if there are docs, they should be attached to the building CCC docs.