I've discovered a great cheat, or rather a glitch/bug in the game... I'm sure many of you didn't get enough house points by the end of the game, so if this was a problem... simply do the following:

do the Incindio challenge for Flitwick, save your game before leaving the class for the quidditch match which Ron tells you about, but after being awarded 40 house points, and then quit and load your game up again. Flitwich is now mysteriously invisible, and will award you another 40 house points!! Repeat until you have enough points. My sister got over 1200 points by doing this! And the house point hourglasses go over 999 and back to 0 again, but Gryffindor still stays in the lead.