A bit lastminute.com, but just to let you know if you're interested in a last minute blast I'm doing a duathlon in France, 10km from Calais on 28th Sept. It's 6.6k 30k 3.4k in a place called Ardres.
Some people from my tri club are doing and have done it before, saying it's a good day out, with a generous goody bag. They say it's an international race, which means mainly French and Belgians (!). Anyway at 12 euros it's good value. It starts at 2pm so was hoping to get the ferry down in the morning and then cycle over to Ardres.
I'll check with the organiser to see if there are anymore places (limited to 350). Entry on the day is possible.
Interested ? Check out http://www.ardresis.com/association/duathlon/
If you don't understand it ask any away, and should be able to help out with transalations.