Tomorrow my water pump is being replaced (under warranty). The reason is that it is weeping oil from the small rubber grommet on the underside. Not much, but any amount is unacceptable thankfully.
Apparently the grommet is an exit for either oil or water if there is a leaking seal, so that either system is non contaminated. I guess that any leakage indicates a failed seal.
The dealer said they had not seen this on any of these engines before (in any of the s1000 forms). I have read on a forum of someone having a coolant leak from the same place but this failure does seem pretty rare.
Fortunately the rest of the bike is going like a train. Still great fun.