Got my bit of chocbox... going to fit it this evening. Will be just stuffing the earth wire into one end of the chocbox and nothing in the other side, thereby 'terminating' it safely. If the light fitting works and all is OK, I'm going to go get some more and replace the awful finickety ones - with various parts that fall out the bottom and three connections - with these ones that seem a much better design... they're very cheap and the zone limitation is fine...
http://www.screwfix.com/p/lap-fixed-round-mains-voltage-bathroom-downlight-brushed-chrome-240v/78571
http://www.screwfix.com/p/lap-fixed-round-mains-voltage-bathroom-downlight-brushed-chrome-240v/78571