Thanks Jason for the prompt reply and assistance.
One parting question, the header use also cancels a metafresh on the thankyou page (tested currently as the condition found) after the download code is executed?
Just to outline my current working flow:
1) Order page which sends out email and redirects to:
2) Thank you page which uses a meta refresh to then call the separate download page:
<meta http-equiv="Refresh" content="1;URL=downloadDemo.php" />
This still leaves us on the Thank you page even thought the meta refresh fires and the download starts.
Expected next step IF wanting to then go home after 5 seconds:
3) use a JS timer to then fire and move to home page unless the meta refresh has also killed any further page processes