ELECTRICITY KILLS Get someone who KNOWS what they are dooing not someone who THINKS they KNOW.
And Yes you can still use the double pole switch
It sounds like your wiring is of an older property.
The green and yellow are Earth wires.
The 3 reds are probably the live feed, a loop from the live to another light. and the 3rd wire will probably go to your light. The neutral black wire should be at the light also.
BUT BE CLEVER GET AN ELECTRICIAN TO FIX IT
pete, July 2008