I think the 70mm dia is going to be a problem if you need that much as the spindle bore. I quite like the idea of making your own from scratch as D.C. suggests. At the end of the day, a lathe is only a driven chuck and 2 axis, so something like the one in the youtube video is very much doable at home. The cost of parts is basically a CNC kit plus a motor and a VFD. I reckon you could make something real nice for less than £1000.