Indeed, and there probably is a Culture ship called the Pretentious Twaddle, possibly run by a Mind forced to listen to Dark Side Of The Moon. Though I rather like the idea of the Culture being one of the UF universe's innumerable precursor races.

Earthforce scouting parties could've found the GSV drifting in an asteroid field on the Coreward Frontier. They then towed it back to Earth under cover of spacefold and got a few of the systems to work, bludgeoned the Mind into submission, cannibalised bits of interesting tech (obviously the things the haven't got working yet) and filled it up with enough guns to render an Alabaman needing quite a long lie down with some tissues. Then the Culture show up in the form of an extremely confused bunch of Special Circumstances agents turning up in Gryphon's front garden, see what Earthforce have done to that poor, defenceless little trillion-tonne... city-ship... and then all Muspelheim breaks loose. Not literally, though. On the other hand, that could be quite fun...