Finally got prototype working and have captured over 90,000 frames with promising results.
Noticed along the way that SMD component tapes fit the 16mm film sprocket really well, so there is food for thought!
Documenting an outline of build and all the useful stuff from around the web that helped me out on my blog, see http://http://usabledevices.com/2014/08/telecine-simple-cheap-prototype-in-action/ movie and photos and all telecine posts (3 so far) http://http://usabledevices.com/category/project-or-device/telecine/. Code is in github http://https://github.com/spanner888/UsableDevices/tree/master/MovieFeedControl.
Next steps are to reduce sprocket wobble and improve film feed in tension - these are both causing movies to wander up and down, film cleaning, post processing (dust removal, colour correction, stabilisation, ....) and maybe a machine vision camera and syncing for faster processing.