You have a problem.
1r and 1 b with 1e will probably be from the mains
a second set will possibly be out to other light units.
then 1R and 1B I would of thought would be to the switch. But that leaves you with 1 extra B. Do you have a timed fan in the bathroom? that could explain the extra. Basically, you need reds connected, then, the black from the switch, would go to one side of the new light, (THAT WOULD BE LIVE) when light is ON. the other side of new light would go to the other blacks. EXCEPT, FOR THE EXTRA BLACK.
BUT WHICH ONE? Unless you have test equipment, Get someone in.
Sheepdog, March 2011