Hi again, sorry I haven't been able to keep you up to date the past few weeks. Now that schools back I'm much busier and work has slowed to the weekends and morning/afternoon either side of school. Jeff here's one of my drawings of the focuser.
The edge of the paper represents the edge of the light path, the long line represents the side of the OTA, the rectangle is the drawtube and the shorter lines are where my eyepieces come into focus. The thick line is where the draw tube ends, and the three circles are the three pairs of bearings. (sorry there's so many lines
Since the shorter lines (where the eyepieces come into focus) over lap when I move the rectangle along I take it there is enough travel to fully focus and I can put the focal plane 16mm out from the OTA.