Summary

I have my Ormerod 1 extruder cooling fan screwed directly onto the fins of the heat sink. This duct simply pushes on to the side of the heat sink and directs some of the air down close to the part/extruder nozzle to provide a bit of cooling - necessary when printing PLA. It is easily clipped into place and removed. It is nothing special, but might solve someone's problem!
14/6/2017 I have updated the part to a better design with more air going to the end of the nozzle.