I actually found that shortly after posting thanks, but I've still got problems. Admittedly I'm not following the howto word for word, but I'll be doing that tomorrow. The installation falls over when it tries to write to /tmp, which is the session.save_path for php. It says the file does not exist, when it does (and all permissions are correct).
I installed successfully on CentOS 4.3, and experimented by changing the path to where it was for CentOS, but the install cannot find that either.
Many thanks for your help.