Attending the Brit Awards 2010. Need Help!!!?

I'm going to the Brit Awards tomorrow (show only guest) and I was wondering if anyone that had been could let me know what the best time is to celeb spot on the red carpet? We have to be seated by 7.45pm but the celebs get dinner beforehand so therefore must arrive earlier. Does anyone know what time they start arriving? I want to stand outside & try and get some autographs. Any help/advice gratefully received x