I did some more work on this machine recently (new house and new garage!). I got the machine to cut out new Y and Z axis & gantry parts, but I changed the design slightly to incorporate LM20UU linear bearings (instead of the skate bearings on the Y and Z) and 20mm linear shaft (instead of the gas pipe). I also changed the lead screws from M8 threaded rod to 12 mm trapezoidal thread. The router holder is also changed for an aluminium one bought off e-bay. First signs are that the machine is more rigid and faster.
I also built an enclosure to keep the dust and noise down (with 6mm thick polycarbonate window), and I am working on a dust extraction system.