The Leaky Cauldron had a nice blurb featuring Chris Rankin (Percy).
http://www.the-leaky-cauldron.org/2009/11/4/the-prodigal-son-returns-chris-rankin-filming-as-percy-weasley-for-deathly-hallows
So bittersweet. This must mean they'll be filming Fred's death, too. I'll need at least a box kleenex for this movie!