Used the Address:
Independant Talent Group LTD
Oxford House
76 Oxford St
London, W1D 1BS
U.K.
I'm on the fence concerning authenticity. I read on google that him and Nicole Kidman are in Edinburgh right now, so that leads me to think its possible that he signed it. I also read this http://www.fanmail.biz/mboard/viewtopic.php?t=209990 and I think my signature matches the one this person has. But, on the flip side it came back in 2 weeks, which seems a little bit too fast for him.
Comments and opinions on authenticity are welcome, however, please don't comment unless you've put some thought into it. If you think its a secretarial please tell me why, don't just post and tell me its a sec.
Here is the picture:

Here is the envelope:
