Hi AussiePete
Many years ago I was in the same situation thinking of building a small lathe. And at that time I found an article i M.E. Vol.150 No.3704 – Vol. 152 No.3730 (1983-84) – about a building project of: "A 2 5/8 in. Centre Lathe" – "A Design for Home Construction Using Stock Materials" by J. Neave. 2 5/8 in centre height, 1 1/2 in over cross slide, 9 1/2 in between centres 27in overall length, approx. 65 lbs weight.
I eventually ended up buying a Sherline lathe instead, much quicker, life is short and project list tooo long 
Lars