its having a false ceiling under the original ceiling so the original rose will be totally hidden. what are you supposed to do in this situation? i can wire the new cable into the original rose switch live and neutral but then you never get to it when its been plastered.
if up then i'd pull cables into loft space, jb them and feed a new switched live/neutral/cpc to my two new lights, make sure new ceiling allows enough room for them, 110mm for fire-rated, or click do a range which are 65mm, they should be used if the room above is habitable, i.e. bedroom
if downstairs use the same method jb under floor above, mark floorboard, maybe even write on exposed grey cable at new light 'jb above' for the future