A couple of photos to accompany my previous description
Ridiculous greenhouse disco lighting! (And yes, that's a lightup ceramic chicken windchime, on the right hand side)
This is the actual system- big fan and tubing down the manifold (a blue barrel).
Some of the things I'm growing
Lemons
Figs
Coffee beans almost ready!
Unfortunately the peak is only 2.5m tall so I haven't got room for a banana. 2.5m is the limit here without having planning permission (which would have confused the planners utterly, and cost me £600)
Have yet to see if these things will all survive winter (the fig and lemon survived in my old non-heatsink greenhouse so they should be fine!)