Here is a email response I received from Ricky Gervais' agent.
Ricky Gervais
Georgia House [
GHouse@unitedagents.co.uk]
[Reply] [Reply All] [Forward]
Actions
In response to the message from Michael Santiago, 10/3/2014
To:
Michael Santiago
Monday, October 06, 2014 5:48 AM
Dear Michael,
Thank you for your email
All fan mail, autograph and charitable requests should be sent to the client care of our postal address. All autograph requests should include a stamped, self-addressed envelope for any reply, no emails or phone calls please. Only envelopes with the correct postage attached can be returned, please do not send money, cheques or vouchers.
We do take the utmost care with client mail but cannot guarantee a reply, chase replies or accept responsibility for any items sent.
Kind regards,
Georgia
Georgia House
Duncan Hayes' Office
cid:EB584CEE-A1D8-4D8D-8FC7-0230EEA71FA3@config
12-26 Lexington Street
London
W1F 0LE
For what its worth, when writing to clients of Independent Talent Group you can include money including USD instead of trying to get british stamps. They usually tell you to include $5.00 USD.