Hmmm. It's not a correct calculation, but my feelings (depending on Jeff's great work) say that:
150 - John Hurt as Mr. Ollivander
150 - John Cleese as Nearly Headless Nick
200 - Warwick Davis as Goblin Bank Teller
200 - Joshua Herdman as Gregory Goyle
250 - Ray Fearon as Firenze
250 - Geraldine Somerville as Lily Potter
250 - Leslie Phillips as The Sorting Hat
250 - Ian Hart as Professor Quirrell
300 - Alfred Enoch as Dean Thomas
300 - Matthew Lewis as Neville Longbottom
400 - Luke Youngblood as Lee Jordan
500 - Adrian Rawlins as James Potter
500 - Warwick Davis as Professor Flitwick
500 - Devon Murray as Seamus Finnigan
Well, or near to that.
