There is a single phase 6 1/2" Holbrook lathe (probably a C13 or T13 - see ) in the Feb issue EIM for less than UKP600. I would snap it up if I had the space even if it did mean losing my beloved Holbrook B8.
As far as I know all old Holbrooks were to very high spec' including an NPL certificated lead screw. Screw cutting is of course separate from fine feed with a micro-adjustable dog clutch operated by carriage position. A joy which certainly takes a lot of the sweat out of screw-cutting.