OK Look at this i found this site apparently its the biggest site on Hp roumers movie stills pics and stuff. It has pictures of all the cast roumered cast etc and what they look like in the film. you should really look at it. ummhere it is:
http://www.the-leaky-cauldron.org/
It is really good
got stuff in it like umm in the books Snape is meant to be 35/36
and in the cast the oldest of the children is actually Tom Felton (who plays Draco Malfoy) who is thirteen.