The water pump in an R is not in the timing cover like it is on the bigger engines, So I don't see how that would cause water in the oil.
Its either the head gasket or a crack/pinhole somewhere. Hope its the gasket. I have seen one block the cracked above the piston (Think it froze) and have a 206 power unit that has a crack in one of the exhaust ports.(really blew water the one time I had it running.) Another place to look is behind the rocker arms.