Thanks everyone for your replies - you've made me laugh.
Perhaps we should have a massed stinky dog walk one day, with a mobile dog groomers at the end of the walk to meet us.
She was back at it today, one minute chasing her ball and then in a split second on her back doing what she does best. Not sure what it was - but the smell in the car was horrendous.
The funny thing is, that Alfie (our Tibetan Terrier) thinks it looks like great fun and so joins in with his paws up in the air - fortunately he hasn't worked out the purpose and so just does it on the grass next to her and not in anything offensive. Its really funny.
I'm resigned to the fact that Poppy is a Cocker who loves all things smelly, dirty, dead, rotting, muddy or wet.