<p>Coming from a desktop background I'm not sure exactly how to pass the exceptions I have caught to an Error page in order to avoid the standard exception screen being seen by my users.  </p>

<p>My general question is how do I pass the exception from page X to my Error page in ASP.net?</p>

I think you can use the
global.asax
--
Application_Exception
handler to catch the exception and then store it for displaying in an error page.
But actually, your error page shouldn't contains code that might cause just another error. It should be simple "Oops! something went wrong" page.
If you want details on the error, use Windows' events viewer or
ELMAH
or employ some logging mechanism.