Here are the top ten Celebs i recomend writing to :

1. Oliver and James Phelps - quick Reply and normally personal.
2. Rob Pattinson - Very quick reply- 2 weeks, personal and great for HP !
3. Keira Knightley - Very famous, reply within 2-3 weeks !
4. Robbie Coltrane - Very quick reply , great for any HP fan
5. Alan Rickman - Personal reply, takes a while - 2 months, big for HP !
6. Kenneth Branagh - Quick reply, personal, HP
7. Matthew Lewis - Reasonably quick reply - 3-4months, personal great for HP !
8. Fiona Shaw - Very quick reply - 2 weeks.
9. Davina McCall - Very quick reply - one week.
10. Rowan Atkinson - Takse a while but definatly worth the wait ! A brilliant actor.

So why not try writing to these people as they are sure to give you great quick reply's :)