I don't seem to have achieved much in the last week as I have been waiting for a few things to arrive. I have managed to mount the extruder on the bottom bracket that previously held the milling drill. I had planned to do that to make it easy to swap between the two, so I used a smaller diameter PTFE rod for the thermal barrier to allow it to fit through the same hole as the drill. What I forgot was that the wires would also have to pass through the same hole! It is a tight squeeze as you can see. The heater wires actually have some plastic insulation where they pass through the aluminium, I hope it doesn't melt!
Another thing I forgot to allow for is that I had to mount the extruder clamp on standoffs to clear the bolt heads and leave space for the wires to exit. Unfortunately that means the nozzle doesn't quite reach the XY table so whatever base material I decide to extrude onto will have to be at least 5mm thick.
On the left of the nozzle you can just see a small thermistor to measure its temperature. The recommended part from RS is on back order but one of my fellow reprappers called englewood was kind enough to send me the alternative one you can see. I hope to repay him with some HDPE extruder parts if my machine is successful at making them.
I attached it by filing a flat on the barrel and clipping it with a couple of coils cut from a small spring. I used a little thermal grease between the two.
The next step is to calibrate the thermistor and see if it will extrude.