I tried creating a custom class and then tried creating a custom style. But
I found the easiest to be the following;
#+AUTHOR: <author>
#+LATEX_HEADER: \newcommand{\orgauthor}{<author>}
#+EMAIL: <email>
#+LATEX_HEADER: \newcommand{\orgemail}{<email>}
#+TITLE: <Title>
#+LATEX_HEADER: \newcommand{\orgtitle}{<Title>}
#+DATE: <Date>
#+LATEX_HEADER: \newcommand{\orgdate}{<Date>}
Then in my custom Latex title page;
#+LATEX_HEADER: \input{template}
I use \orgauthor{} etc. for the relevant fields.
Works very well, apart from the duplication of author, email, date etc.
It would be great if org-mode added support for substitution to the #+
fields.