Sorry guys, for not replying to this thread earlier. I had a new baby boy this summer (unexpectedly popped out 6 weeks early), so Porsche stuff hasn't really been on my mind!
Thanks for all the responses, and especially to roadracer for being the guinea pig! My cover isn't REALLY dirty, but it has gotten quite dusty. I ended up giving it a good shake out last week, and put it onto the car for the winter.
I will try washing it in the front load in the spring!
cheers