http://the-shg.org
Whatever you do, don't talk to him or let him in. He is only there to find a reason to prosecute. If hecan'tfind one he will try to find reason to issue an improvement notice. Once he has done that if you then don't comply or let him in he has reason to ask the police to get a warrant for entry.
Talk to the SHG on 0744 99 89 411.
Other sites with information on the RSPCA
RSPCA-Animadversion
http://rspca-animadversion.org.uk
The SHG Blog
http://theshg.wordpress.com
RSPCA Injustice Blog
http://www.rspcainjustice.blogspot.com/
SHG Press release