Hmm, I'm not so sure I'd be willing to ignore the lack of annual services on a car with low annual mileage. Sure if the annual service more or less coincides with the mileage service, then that's one thing, but a low mileage car could go two or more years without any fluids being changed, or any adjustments being made, and that would worry me, particularly on an engine that is now ten years old, and one that's a prima donna at the best of times. For me, as time passes, it's increasingly important to see paperwork showing a well cared for engine appropriate to the time between services rather than the mileage between services.
Don't forget the GT series engines are much newer engines and engineering tolerances have improved markedly in recent times, as have the materials used to make them. Likening the 4200/GS engines to the later GT engines is, for me, a dangerous comparison to make, and I wouldn't be at all convinced to view a 4200/GS car that has followed the later service routine.