Oh dear.
No, no, no... I'm being INCREDIBLY unclear lol.
James Hannigan scored the fifth and sixth Harry Potter games, but none of the others.
Nicholas Hooper scored the fifth and sixth films. Hooper tends to move away from what THE GREAT Mr. Williams did with the music.
James Hannigan not only returned the series to using John William's themes effectively, he has created new themes using John Williams original.
So, while Hooper abandons John Williams, Hannigan has done great work by being faithful and creating variants on the original themes.
If you were to listen to the soundtracks, you'd hear a bit of that... but unfortunately, the soundtracks don't contain anything that sounds "John Williamsy" because of copyright restrictions. If you want the whole James Hannigan experience, play the actual games... They're awful, but the music is awesome.
Hannigan's opening Theme in the soundtrack is A LITTLE like Williams. You can hear amazing similarities. Plus it is amazing. Check it-outify:
http://www.youtube.com/watch?v=q8celd-INyE,
The mods are gonna hate me... I'm terrible about staying on topic.