By "no visible colours" do you mean black?
Was the plastic ceiling rose held in place with two M4 machine screws?
If you have the wiring arrangement I'm thinking of there should be a threaded hole in the steel box which the wires come out into which you can use as an earthing point using a short (10mm or so) machine screw, ring crimp and short (100mm or so) length of 1mm or 1.5mm earth wire, which you could probably get from an extension lead.
If you're not going to run an earth loop test (I am assuming you don't have the correct tester) it may be safer to draw a new earth lead back to the consumer unit using a draw wire, which should cost under a tenner. (make sure you isolate the board using the main switch). Depending on how far the light is from the consumer unit this could be a time consuming process.
*Remember I haven't personally seen any of this so my advice can't be taken as definitive*
I don't like saying this on a DIY forum but unless you feel competent to a fairly advanced level i would suggest calling in an electrician who also does commercial and industrial work.
Adam
February 2010
howtomendit.com for free repair help, information and advice.
