More spellings of gimbal than there were answers!! How about gymbal???
Cheeky monkey grounded. I've worked on INS systems (admittedly years ago) and I'm not yet 50!
Low n' Slow - you need to study your gyro theory a little more as you've almost answered your question. Rate gyros are NOT free to precess about their axis, they're restrained such that their angular output corresponds to an angular RATE of change.
In an INS (lets exclude the Delco carosel as it had a rotating platform to help eliminate long term errors, although the principle is the same) the outputs of these rate gyros are used to operate motors on the platform gimbals (NOT the gyro) which maintained the alignment of the platform irrespective of the attitude of the a/c. This meant that to all intents and purposes the gyros didn't move because as soon as the gyro produced an output, the correction was sent to the respective platform gimbal motor which corrected the platform and nulled the gyro.
The 3 gyros each have their axis and gimbal position, such that they sense movement in a particular plane. 2 spinning horizontally (i.e. a vertical spin axis) but with gimbals positioned to sense pitch and roll and the 3rd spinning vertically (horizontal spin axis) to sense directional changes.
What you could get however, was PLATFORM gimbal lock. Usually the chances of this were reduced by adding a 4th driven gimbal which maintained angular separation of the inner gimbals.
Hope this helps a little.