I would hesitate to put the 'Sir Peter Maxwell' character in the same category as sites such as theonion.com as I feel they just recycle the same "spoof news" stories over and over. There are thousands of those sites out there and they don't really do anything for me.
Personally I feel www.sirpetermaxwell.com pushes the boundaries of good taste but it is hard to suggest that it's not funny (in my opinion anyway). But maybe i'm just sick in the head