Hi there,
This is because there is possibly not switch wire.
The 3 sets you mention are for the following;
1 set goes to the switch
1 set comes from another light in another room
1 set goes to another light in another room, these 2 sets are the "loop" circuit.
To connect the new light up I would get a small 4 way junction box (5amp) type if there is room or use medium terminal blocks.
Turn the electric off first tho & take the red wires that are joined togerther in the old rose out & connect to 1 terminal in either the blocks or junction box.
The earth wires are all connected together so again use another terminal for these.
The black wires that are joined together in the old rose should have 1 going to the old lamp, again connect them together in 1 block & the remaining wire that goes to the other side of the old light connect up to the spare wire you have left.
Earth the new light & this should sort it out for you.
Rob, July 2007