Yes metal downlighters will need earthed. The earth in a flat grey cable might well have been cut back and/or it may not be sleeved, ie it will be bare copper. You can see if it has been cut back if there is any slack in the wire to pull through and examine where the red/black wires meet the grey sleeving. . . but never force the cable in any way and always turn off at the fuseboard/consumer unit before going near any wiring. I am assuming there is only 1 flat cable connecting at the rose, if there are more they should all be connected to a common earth terminal inside the ceiling rose. I would not advise taking an earth from anywhere else, especially in a bathroom. Oh yeah, if the downlighters are SELV then they may not need earthed after all . . .
tim
April 2007