Just a quick post to an old post! - The "missing link" for me was a reliable actuator controller. This finally came in the shape of a Pololu Jrk 12v12 USB "Motor Controller with Feedback" http://www.pololu.com/catalog/product/1393
The Pololu JRK has been a joy to program and to use. My gearbox travel was only c. 35mm, but the resolution of the controller provides extremely fine control.
Not a single missed gear change.
I shall be looking to change the input values via TTL serial rather than analogue in - just to add soem additional "safety" logic for no changes to Park or Reverse without the brake being pressed. Nothings happened as yet, but this may just complete a very satisfying project that has released a good deal of interior space now taken by a Asus EP121 ( different league to anything I've installed to date - Boe Hydis screen being a good example).
No time for photos, but just thought I would send an update with regards the Pololu controller...