This may not help - but our 04 25 has been in the family since new and has enjoyed 3 new batteries so far. When it had only done 8000 miles.
It was checked by the dealer under warranty but they said nothing wrong. Last year I had another garage check it at MOT time and , you guessed it, nothing wrong.
I am not mechanical but I suspect it's to do with the alarm/immobiliser and expect to be back to the garage soon as I am fed up with charging the battery.
So I hope you get a response to your question soon!!
Rod
May 2009